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Robust sliding mode‐based extremum‐seeking controller for reaction systems via uncertainty estimation approach
Get PDF"This paper deals with the design of a robust sliding mode‐based extremum‐seeking controller aimed at the online optimization of a class of uncertain reaction systems. The design methodology is based on an input–output linearizing method with variable‐structure feedback, such that the closed‐loop system converges to a neighborhood of the optimal set point with sliding mode motion. In contrast with previous extremum‐seeking control algorithms, the control scheme includes a dynamic modelling‐error estimator to compensate for unknown terms related with model uncertainties and unmeasured disturbances. The proposed online optimization scheme does not make use of a dither signal or a gradient‐based optimization algorithm. Practical stabilizability for the closed‐loop system around to the unknown optimal set point is analyzed. Numerical experiments for two nonlinear processes illustrate the effectiveness of the proposed robust control scheme.
Influencia del carbono en la transformación martensítica de una aleación Heusler Ni-Mn-In
Get PDFTesis (Maestría en Nanociencias y Materiales)"Se estudió el efecto de la adición del carbono en la aleación Ni50Mn35In15, los porcentajes atómicos añadidos fueron 0.1, 0.2, 0.3, 0.5, 0.6, 0.8, 1.0 %. Las aleaciones se sintetizaron a partir de elementos de alta pureza, por fusión en arco eléctrico con una atmósfera inerte de Ar. Las aleaciones se caracterizaron por calorimetría diferencial de barrido, difracción de rayos X, microscopía óptica y microscopia electrónica de barrido; además, se realizaron mediciones de dureza y de cambio de temperatura adiabático. Se encontró que, las temperaturas de transformación martensítica de la aleación disminuyen al adicionar carbono, aproximadamente 40 K para la aleación con 1% at. C. Como consecuencia de este decremento la entalpía y entropía de transformación también disminuyen. La estructura cristalina encontrada a temperatura ambiente para la aleación sin carbono corresponde a una martensita monoclínica con modulación 6M. Para las aleaciones con 0.5 y 1.0 % at. C. hay una mezcla de martensita y austenita. La austenita presenta orden químico y su estructura fue identificada como estructura Heusler del tipo L21. La dureza de la aleación Ni50Mn35In15 fue de 274 HV y aumentó de manera lineal hasta un 10% en la aleación con mayor contenido de carbono (1% at. C.). Se realizó un estudio del efecto elastocalórico en dos aleaciones, una sin carbono y otra con 1 % at. El valor máximo del cambio de temperatura adiabático inducido con esfuerzo uniaxial fue de -3.3 K a Δσ = -80 MPa para la aleación ternaria y -5.2 K a Δσ = -170 MPa para la aleación (Ni50Mn35In15)99C.""The effect of the addition of C in de Ni50Mn35In15 alloy was studied, the atomic percentages added were 0.1, 0.2, 0.3, 0.5, 0.6, 0.8, 1.0%. The alloys were synthesized from high purity elements by fusion in arc furnace under inert Ar atmosphere. The alloys were characterized by differential scanning calorimetry, X-ray diffraction, optical microscopy and scanning electron microscopy; in addition, measurements of hardness and of the adiabatic temperature change were performed. It was found that martensitic transformation temperatures decrease by adding carbon to the alloy, about 40 K for the alloy with 1 at. % C. As a result of this, a decrease the enthalpy and entropy of transformation also decreased. Crystalline structure found at room temperature for the C-free alloy corresponds to a monoclinic six-layered (6M). With increasing C content, the alloys show a mix of martensite and austenite. The austenite phase presented an Heusler structure which corresponds to a cubic L21 type. The hardness of the Ni50Mn35In15 alloy was 274 HV and increased linearly up to 10% in the alloy with the highest carbon content (1 at. % C). Elastocaloric effect measurements were carried out in two alloys, with and without carbon content. The maximum value of the adiabatic temperature change induced with uniaxial stress was -3.3 K to Δσ = -80 MPa for the ternary alloy, and -5.2 K to Δσ = -170 MPa for the alloy (Ni50Mn35In15)99C.
Control híbrido de rectificadores modulados en ancho de pulso
Get PDF"El presente trabajo de tesis se enfoca en el análisis, diseño, implementación y control de un rectificador monofásico PWM (Modulado en ancho de pulso) con estructura de puente completo. El rectificador se analiza utilizando una descripción lineal por pedazos debido a que permite cuantificar y observar las variaciones presentes en el rizo de corriente al ocurrir conmutaciones en los interruptores que lo forman. Utilizando el enfoque de sistemas conmutados integrador se propone un control de tipo conmutado para la corriente de entrada que permite controlarla alrededor de una referencia deseada minimizando la distorsión armónica, compensando el factor de potencia y controlando el ´angulo de desfasamiento entre el voltaje y la corriente de entrada. El control propuesto se basa en el establecimiento de una región de operación y el diseño de una ley de conmutación dependiente del tiempo que permite contener todo posible transitorio de la corriente dentro de esta región evitando la pérdida de estabilidad reportada en la literatura (distorsión de la corriente de entrada en los cruces por cero) a pesar de perturbaciones en la entrada del rectificador o variaciones en el valor de la carga. El control conmutado propuesto en el presente trabajo de tesis se deriva de una análisis de controlabilidad o estabilizabilidad conmutada y es susceptible de ser utilizado en conjunto con un lazo de control de voltaje para rechazar perturbaciones que afecten el voltaje de salida y mantenerlo regulado. Debido a que la pérdida de controlabilidad no está ligada solo a convertidores tipo rectificador, la estrategia de control propuesta permite ser extendida a otros tipos de convertidores que tienen interconexión con la red eléctrica. El desempeño del control conmutado de corriente propuesto en esta tesis en conjunto con un lazo de control de voltaje fue verificado mediante simulaciones y mediante el desarrollo experimental de un prototipo en el Laboratorio de Sistemas Híbridos del IPICyT. Finalmente los resultados numéricos permiten ver las ventajas del control propuesto contra otros tipos de control reportados.""The present thesis work is focused in the analysis, design, implementation and control of a PWM single phase bridge rectifier. The rectifier was analyzed using a piecewise linear description since it allows to quantify the actual ripple current variations given by the switches commutations. Using the benchmark of integrator switched systems, a switched input current control is proposed that allows the control of the input current about a desire reference minimizing the harmonic distortion and controlling the phase between the input current and voltage. The proposed control is based on the establishment of an operation region and a time-dependent switching law that allow to confine every current transient inside of a region, avoiding the stability lost reported previously (input current distortion on the zero crossings) despite voltage sags or load changes. The proposed switched control is derived from a controllability analysis and it is susceptible to be used with an external voltage control loop to reject perturbations and to regulate the output voltage. The controllability analysis can be extended to other converters with interconnection to an AC grid. Both, the switched current control performance and the voltage control loop proposed in this thesis work were verified using simulations and experimental work using a prototype developed in the Hybrid Systems Laboratory of IPICyT. Finally the numerical results allow us to compare the proposed control with other reported control techniques.
Analysis of microRNA expression in newborns with differential birth weight using newborn screening cards
Get PDF"Birth weight is an early predictor for metabolic diseases and microRNAs (miRNAs) are proposed as fetal programming participants. To evaluate the use of dried blood spots (DBS) on newborn screening cards (NSC) as a source of analyzable miRNAs, we optimized a commercial protocol to recover total miRNA from normal birth weight (NBW, n= 17–20), low birth weight (LBW, n = 17–20) and high birth weight (macrosomia, n = 17–20) newborns and analyzed the relative expression of selected miRNAs by stem-loop RT-qPCR. The possible role of miRNAs on the fetal programming of metabolic diseases was explored by bioinformatic tools. The optimized extraction of RNA resulted in a 1.2-fold enrichment of miRNAs respect to the commercial kit. miR-33b and miR-375 were overexpressed in macrosomia 9.8-fold (p < 0.001) and 1.7-fold, (p < 0.05), respectively and miR-454-3p was overexpressed in both LBW and macrosomia (19.7-fold, p < 0.001 and 10.8-fold, p < 0.001, respectively), as compared to NBW. Potential target genes for these miRNAs are associated to cyclic-guanosine monophosphate (cGMP)-dependent protein kinase (PKG), mitogen-activated protein kinase (MAPK), type 2 diabetes, transforming growth factor-β (TGF-β)and Forkhead box O protein (FoxO) pathways. In summary, we improved a protocol for analyzing miRNAs from NSC and provide the first evidence that birth weight modifies the expression of miRNAs associated to adult metabolic dysfunctions. Our work suggests archived NSC are an invaluable resource in the search for fetal programming biomarkers.
Pinus hartwegii Lindl. treeline ecotone: structure and altitudinal limits at Nevado de Toluca, Mexico
Get PDF"Introduction: Treeline ecotone complexity might function as a barrier to altitudinal migration of Pinus hartwegii Lindl. Objectives: P. hartwegii forest structure was characterized through its treeline ecotone at Nevado de Toluca; in addition, possible changes in altitudinal limits over the last 25 years were determined. Materials and methods: Height and diameter at breast height (DBH) of each tree were determined, as well as natural forest regeneration and tree density. Altitudinal limits were determined on satellite images from 1989 and 2014 using the moving split window method. Results and discussion: Tree density fell between 8 and 70 % across altitudinal gradient. Altitudinal limits (3,980-4,130 m) did not show significant differences (P = 0.07) between two evaluated years. The P. hartwegii ecotone displays a diffuse form, regulated by growth limitations. This implies that the forest might modify its altitudinal distribution based on environmental changes, according to its ecological amplitude and how fast new individuals can become established at higher altitudes. Conclusion: Long-term monitoring is important to know if P. hartwegii is actually capable of migrating altitudinally as a result of increased environmental temperature.
Role of indigenous microbiota from heavily contaminated sediments in the bioprecipitation of arsenic
Get PDF"High arsenic concentrations have been detected in alluvial aquifers of arid and semi-arid zones in Mexico. This work describes the potential of microbial arsenate reduction of the indigenous community present in sediments from an arsenic contaminated aquifer. Microcosms assays were conducted to evaluate arsenate and sulfate-reducing activities of the native microbiota. Two different sediments were used as inoculum in the assays amended with lactate (10 mM) as electron donor and with sulfate and arsenate (10 mM each) as electron acceptors. Sediments were distinguished by their concentration of total arsenic 238.3 ± 4.1 mg/kg or 2263.1 ± 167.7 mg/kg, which may be considered as highly contaminated sediments with arsenic. Microbial communities present in both sediments were able to carry out arsenate reduction, accomplished within 4 days, with the corresponding formation of arsenite; sulfate reduction took place as well. Both reducing activities occurred without previous acclimation period or enrichment, even at potential inhibitory concentrations of arsenate as high as 750 mg/L (10 mM). The formation of a yellowish colloidal precipitate was evident when both reducing processes occurred in the microcosm, which contributed to remove between 52 and 90.9% of As(III) from the liquid phase by bioprecipitation of arsenic as arsenic sulfide.
Understanding the dynamics and contamination of an urban aquifer system using groundwater age (14C, 3H, CFCs) and chemistry
Get PDF"The quality of the groundwater supplying drinking water to the Guadalajara metropolitan area has deteriorated due to both endogenic and exogenic processes. Previous studies of this complex neotectonic volcanic environment suggest that the sources of contamination here are underground fluids derived from an active volcanic center and surface wastewater derived from regional land?use intensification. This study uses isotopic, gaseous, and chemical signatures to more comprehensively characterize this groundwater flow and its contamination paths. Groundwater is mainly recharged at the La Primavera Caldera to the west and is discharged into the Santiago River to the east. The exception to this trend is the Toluquilla area, where groundwater most likely represents rainfall originating from outside the basin limits. Evaporation affects groundwater in these areas, especially waters that have been affected by recycling below urban areas in the Atejamac area and by intensive agricultural activity in the Toluquilla area. Additionally, we present evidence that groundwater flow through alluvial sediments and tuffs in deeper wells mixes with a lower aquifer unit in basaltic?andesitic rocks, which are in contact with hydrothermal fluids. Groundwater ages range from postbomb in the western and northwestern regions of the study area (i.e., the Atemajac aquifer unit) to Late Pleistocene in the southern and southeastern regions (i.e., the Toluquilla aquifer unit). Recently recharged water records little mixing and is located mostly in or near the La Primavera volcanic system. As groundwater undergoes gravitational flow towards discharge areas, it mixes with older water components. Chloride and sodium concentrations above natural background levels are primarily related to volcanic activity, nitrate is associated with human activities, and sulfate originates from both anthropogenic sources and water–rock interactions. Nitrate originating from land?use activities (such as sewers, septic tanks, landfills, and agricultural fields) that is introduced into the deeper part of the groundwater system is expected to travel with the groundwater to the discharge areas because oxidizing conditions will prevent microbial reduction.
Modification of AtGRDP1 gene expression affects silique and seed development in Arabidopsis thaliana
Get PDF"Glycine Rich Proteins (GRPs) are induced at different developmental stages and in specific plant tissues. Recently, we described a novel Arabidopsis gene encoding a short glycine-rich domain protein (AtGRDP1). This gene is involved in abiotic stress responsiveness; the Atgrdp1-null mutant seeds were more sensitive to stress, while the opposite phenotype was achieved by AtGRDP1 overexpression. In this study, we analyzed the phenotype of the fruits produced by Arabidopsis Atgrdp1 mutants and 35S::AtGRDP1 overexpression lines. Our analyses revealed important changes in silique length, seed number, seed weight and morphology in the analyzed lines. In particular, Atgrdp1 mutant lines exhibited several defects including short siliques, a diminished number of seeds per silique, and a reduction in seed size and weight as compared to Col-0. The overexpression of the AtGRDP1 gene also generated phenotypes with alterations in size of silique, number of seeds per silique, and size and weight of the seed. In addition, the expression analysis of AtGRDP1 gene showed that it was expressed in floral and fruit organs, with the highest expression level in mature siliques. The alterations in the siliques and seeds traits in the Atgrdp1 mutant line, as well as the phenotypes observed in AtGRDP1 overexpression lines, suggest a role of the AtGRDP1 gene in the Arabidopsis fruit development.
Recreating intestinal peristalsis in the petri dish
Get PDF"Here we describe a culture technique of cells dissociated from the external muscularis of the guinea pig small intestine, which allows us to maintain all the elements involved in the intestinal peristaltic reflex. After a few days in culture, these cells reorganize to form a small group of cells that permit the generation of pacemaker activity, spontaneous contractions, and the development of inhibitory and excitatory junction potentials in the petri dish, all elements involved in the peristaltic reflex. Therefore, these co-cultures are suitable to study the cellular and molecular aspects related to the development, maintenance, and modulation of motor intestinal functions.