Repositorio IPICYT
Not a member yet
1534 research outputs found
Sort by
Estimación de pose y velocidades de objetos en movimiento mediante visión por computadora
Get PDF"Muchos procesos automáticos requieren de la interacción de robots con su medio ambiente, para los cuales la visión computacional es una gran herramienta para el reconocimiento y localización de objetos. En este trabajo se plantea un escenario en el que un brazo manipulador requiere de la interacción con objetos que se desplazan sobre un transportador lineal y se utiliza la visión computacional para calcular la pose y la velocidad de dichos objetos. Esto utilizando una sola cámara para extraer esa información, estableciendo un marco de referencia en la cámara y un marco en las diferentes posiciones observadas del objeto. Para lograr dicha tarea, se utilizan propiedades geométricas para extraer la relación entre dos escenas del mismo objeto, y después esta información es utilizada para estimar la pose del objeto con respecto al marco de referencia de la cámara. Del mismo modo, se muestra la utilización de un observador que estima el error de posición (que es la diferencia en la pose del objeto con respecto a una pose inicial de referencia) que al multiplicar dicha estimación por una matriz Jacobiana afín, se puede identificar la velocidad traslacional y rotacional del objeto.""Many automatic processes require the interaction of robots with their environment, for which the computer cision is a great tool for recognition and localization of objects. This work describes a scenario, in which a manipulator requires the interaction with objects moving on a linear conveyor, and computer vision is used to estimate the pose and velocity of those objects. All of this using a single camera to extract that information, by setting reference frame on the camera and another frame in each position observed of the object. To accomplish this task, geometric properties are used to extract the relationship between two scenes of the same object, and then this information is used to estimate the pose of the object relative to the reference frame of the camera. Similarly, an observer that estimates the position error system (which is the difference in the pose of the object relative to an initial reference pose) is shown, and multiplying the observer estimation by a Jacobian-like matrix, one can identify the translational and rotational velocity of the object.
Production of biodiesel from roasted chicken fat and methanol: free catalyst
Get PDF"Transesterification reactions free of catalyst between roasted chicken fat with methanol were carried out in a batch reactor
in order to produce biodiesel to temperatures from 120°C to 140°C. Parameters related to the transesterification reactions, including temperature, time and the molar ratio of chicken fat to methanol also investigated. The maximum yield of the reaction was of 98% under conditions of 140°C, 4 h of reaction time and a molar ratio of chicken fat to methanol of 1:31. The biodiesel thus obtained exhibited a viscosity of 6.3 mm2/s and a density of 895.9 kg/m3. The results showed this process can be right choice to produce biodiesel since this process does not use any catalyst. Therefore, the steps of neutralization and washing are avoided, indispensables in the case of the alkaline catalysis.
Enhanced refrigerant capacity in two-phase nanocrystalline/amorphous NdPrFe17 melt-spun ribbons
Get PDF"he magnetocaloric properties of NdPrFe17 melt-spun ribbons composed of nanocrystallites surrounded by an intergranular amorphous phase have been studied. The nanocomposite shows two successive second-order magnetic phase transitions (303 and 332 K), thus giving rise to a remarkable broadening (approximate to 84 K) of the full-width at the half-maximum of the magnetic entropy change curve, Delta S-M(T), with a consequent enhancement of the refrigerant capacity RC. For a magnetic field change of 2 T, vertical bar Delta S-M(peak)vertical bar = 2.1 J kg(-1) K-1 and RC = 175 J kg(-1). Therefore, the reversible magnetocaloric response together with the one-step preparation process makes these nanostructured Fe-rich alloy ribbons particularly attractive for room temperature magnetic refrigeration.
Global finite-time stability characterized through a local notion of homogeneity
Get PDF"In this work, a notion of local homogeneity is formally defined. Important results involving homogeneous functions or vector fields are reformulated in the consequent local context. In particular, global finite-time stability is characterized through the proposed notion of local homogeneity. As an application of the developed analytical setting, a global finite-time stabilization scheme for robot manipulators with bounded inputs is presented. The developed framework and results prove to be useful to relax analytical and synthesis constraints imposed or generated by homogeneity requirements.
One-parameter families of supersymmetric isospectral potentials from Riccati solutions in function composition form
Get PDF"In the context of supersymmetric quantum mechanics, we define a potential through a particular Riccati solution of the composition form (F ◦ f)(x) = F(f(x)) and obtain a generalized Mielnik construction of one-parameter isospectral potentials when we use the general Riccati solution. Some examples for special cases of F and f are given to illustrate the method. An interesting result is obtained in the case of a parametric double well potential generated by this method, for which it is shown that the parameter of the potential controls the heights of the localization probability in the two wells, and for certain values of the parameter the height of the localization probability can be higher in the smaller well.
Trends in nanoscience, nanotechnology, and carbon nanotubes: a bibliometric approach
Get PDF"Carbon nanotubes are currently one of the most important materials due to their strong mechanical resistance, light weight, and transport properties. Since the publication of Ijima’s paper on tubular carbon structures (Iijima, Nature 354:56–58, 1991), approximately 80,000 research articles have been published according to the ISI web of science (WOS) database, using “carbon nanotube*” as the search criterion in the search by topic option. In this work, the development and impact of nanoscience and nanotechnology (N&N) and carbon nanotubes on several research areas, journals, specific papers, and emerging research areas are analyzed and discussed. Considering the production of papers in these areas from 1997 to 2012, quantitatively speaking, the People’s Republic of China is emerging as the leading country in N&N and carbon nanotube research, passing the United States of America. WOS data analysis of nanoscience, nanotechnology, and carbon nanotube research in developed and developing countries is discussed, and some ideas for accelerating the progress in these important research areas are proposed.
Shifted one-parameter supersymmetric family of quartic asymmetric double-well potentials
Get PDF"Extending our previous work (Rosu, Mancas, Chen, Ann.Phys. 343 (2014) 87-102), we define supersymmetric partner potentials through a particular Riccati solution of the form F(x) = (x − c)2 − 1, where c is a real shift parameter, and work out the quartic double-well family of oneparameter isospectral potentials obtained by using the corresponding general Riccati solution. For these parametric double well potentials, we study how the localization properties of the two wells depend on the parameter of the potentials for various values of the shifting parameter. We also consider the supersymmetric parametric family of the first double-well potential in the Razavy chain of double well potentials corresponding to F(x) = 1/2 sinh 2x−2 (1+p2) sinh 2x/(1+p2) cosh 2x+1 , both unshifted and shifted, to test and compare the localization properties.
The relevance of burial to evade acorn predation in an oak forest affected by habitat loss and land use changes
Get PDF"Seed burial was proposed as an effective mechanism to evade seed predation in continuous forests. However, the relevance of burial as a mechanism to evade seed predators may be compromised in fragmented forests intensely affected human activities because: (1) predators are usually concentrated within forests patches and this may elevate consumer pressure on seed banks at these habitats; and (2) fragmentation reduces seed production in remnant trees and this then decreases the availability of resources for seed consumers. Thus, seed predators within forest patches might be forced to consume buried seeds after seeds on the soil surface are depleted. Indeed, they may even explore the surrounding matrix habitat in search of food when seeds within the patches become scarce. This study assesses the relevance of burial as a mechanism to evade seed predators in a fragmented oak forest from central Mexico where human activities have generated four habitat types: the interior of remnant forest patches, their edges, the matrix habitat surrounding the patches, and an abandoned agricultural field in the neighborhoods of the fragmented forests. We experimentally assessed removal rates of acorns exposed on the soil surface and buried acorns in all these habitat types and compared them. Our results indicated that acorn burial may be an effective mechanism to evade predation in habitats strongly affected by human activities (e.g., the matrix surrounding the forest patches or the abandoned agricultural field), while it would have little relevance within forest patches.""El enterramiento de semillas es considerado un mecanismo efectivo para evadir la depredación en bosques continuos. Sin embargo, su importancia puede verse comprometida en bosques fragmentados debido a que: (1) los depredadores suelen concentrarse en los parches de bosque, lo que eleva la presión de consumo sobre las semillas; y (2) la fragmentación reduce la producción de semillas en los árboles remanentes, lo que disminuye la disponibilidad de alimentos para sus consumidores. Así, los depredadores podrían verse obligados a consumir semillas enterradas después de agotar las semillas en la superficie del suelo. De hecho, podrían incluso explorar el hábitat circundante en busca de comida cuando las semillas dentro de los parches escaseen. Este estudio se enfoca en estos temas en un encinar fragmentado, donde las actividades humanas generaron cuatro tipos de hábitats: el interior de los parches de bosque, sus bordes, la matriz de hábitat que rodea los parches, y un campo agrícola abandonado colindante al bosque fragmentado. En este paisaje se evaluó cuáles animales contribuyen a movilizar las bellotas, y se compararon las tasas de sustracción entre bellotas enterradas y expuestas en la superficie del suelo a través de esos tipos de hábitat. Ratones del género Peromyscus y aves del género Aphelocoma fueron detectados sustrayendo bellotas en todos los tipos de hábitats, pero los ratones sólo se registraron durante la noche mientras que las aves sólo se registraron durante el día. Las bellotas enterradas fueron menos sustraídas (12-35%) que las expuestas (42-68%) en el hábitat de la matriz y el campo abandonado. Sin embargo, dentro de los parches de bosque y sus bordes, las bellotas enterradas (78-81%) y expuestas (91%) no mostraron diferencias en sus tasas de sustracción. Estos resultados sugieren que el enterramiento puede ser un mecanismo eficaz para evadir la depredación de bellotas en hábitats fuertemente afectados por las actividades humanas, mientras que tendría poca relevancia dentro de los parches de bosque.
Paleozoic exotic blocks of the crimean mountains: stratigraphy and origin
Get PDF"Based on numerous geological data obtained by the authors for several decades, the stratification of Permian and Carboniferous ancient and exotic blocks of Crimean Mountains is performed. The sequence of geological events that cause their origin is revealed. Carnian-Norian, Rhaetian-Hettangian and Early-Pliensbachian phases of collapse, sliding and burial of Paleozoic blocks are specified. Final stage (block re-deposition) is confined to the Toarcian and Aalenian ages. The data obtained allow re-interpreting the origin of ancient exotic blocks of the Crimea.
