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Design of a flexible analog signal conditioning circuit for DSP-based systems
Get PDF"This paper presents the design of a flexible analog signal conditioning circuit (SCC) able to be reconfigured de- pending on user requirements. The SCC can be employed with DSP-based systems. The design is aimed to be used in power electronics applications where a wide range of signals types are present. In order to guarantee reconfiguration, the design is constituted of interconnected stages that can be activated depending on the characteristics of the input signal. The proposed circuit is a simple and a low cost solution because it employs off-the-shelf components.
Further results on exponential stability of linear continuous time difference systems
Get PDF"This paper provides further Lyapunov results for the exponential stability of linear continuous time difference system involving discrete and distributed delays. We consider such a class of systems in the case when the discrete and distributed delays are independent thus completing the recent Lyapunov results obtained for the case when the delays are dependent.
Strobilus and seed production of Dioon edule (Zamiaceae) in a population with low seedling density in San Luis Potosí, Mexico
Get PDF"We describe strobilus and seed development in a Dioon edule (chamal, palma, dameu') population characterized by low seedling and high adult tree density, in order to improve conservation decisions for this endangered cycad species. Female strobili required 16-17 months and male 4-5 months to develop. During this period 80% female and 100% male strobili were not damaged by herbivores. The method of cone analysis used to evaluate seed production of pines was modified for D. edule, providing actual yield of individual strobili compared to potential seed yield, explaining productivity in terms of seed efficiency, and identifying and quantifying the types of seed failures. Larger strobili have higher seed potential calculated as the number of seeds potentially produced in the fertile megasporophylls of each strobilus, total seeds actually produced, and seeds with an embryo (filled). Calculated average seed potential per strobilus was of 230.4 seeds. Using the X-ray technique, average seed traits were 100.2 full, 1.8 insect damaged, and 0.6 malformed. Seed efficiency (number of filled seeds as a percentage of the seed potential of each strobilus) of 42.5% indicated that major seed loss was attributable to abortive ovules and seeds, possibly due to ineffective pollination. Seedling survival in greenhouse conditions was 100% after one year. Low seed production affects the population structure and hinders its conservation.
Output-feedback adaptive SP-SD-Type control with an extended continuous adaptation algorithm for the global regulation of robot manipulators with bounded inputs
Get PDF"In this work, an output-feedback adaptive SP-SD-type control scheme for the global position stabilization of robot manipulators with bounded inputs is proposed. Compared with the output-feedback adaptive approaches previously developed in a bounded-input context, the proposed velocity-free feedback controller guarantees the adaptive regulation objective globally (i.e. for any initial condition), avoiding discontinuities throughout the scheme, preventing the inputs from reaching their natural saturation bounds and imposing no saturation-avoidance restrictions on the choice of the P and D control gains. Moreover, through its extended structure, the adaptation algorithm may be configured to evolve either in parallel (independently) or interconnected to the velocity estimation (motion dissipation) auxiliary dynamics, giving an additional degree of design flexibility. Furthermore, the proposed scheme is not restricted to the use of a specific saturation function to achieve the required boundedness, but may involve any one within a set of smooth and non-smooth (Lipschitz-continuous) bounded passive functions that include the hyperbolic tangent and the conventional saturation as particular cases. Experimental results on a 3-degree-of-freedom manipulator corroborate the efficiency of the proposed scheme
Elastocaloric and magnetocaloric effects in Ni-Mn-Sn(Cu) shape-memory alloy
Get PDF"We have studied magnetocaloric and elastocaloric properties of a Ni-Mn-Sn(Cu) metamagnetic shape-memory alloy undergoing a magneto-structural transition (martensitic type) close to room temperature. Changes of entropy have been induced by isothermally applying both mechanical (uniaxial stress) and magnetic fields. These entropy changes have been, respectively, estimated from dilatometric measurements giving the length of the sample as a function of temperature at selected applied forces and magnetic fields and from magnetization measurements as a function of temperature at selected applied magnetic fields. Our results indicate that the elastocaloric effect is conventional and occurs in two steps which reflect the interplay between the martensitic and the incipient magnetic transitions. By contrast, the magnetocaloric effect is inverse and occurs in a single step that encompasses the effect arising from both transitions.
Analysis of phthalic acid, bisphenol A and bisphenol A dimethacrylate in Mexican food cans by HPLC with evaporative light scattering detector
Get PDF"Bisphenol A (BPA), bisphenol A dimethacrylate (BisDMA) and phthalic acid (PA) endocrine disruptors can migrate from the plastic lining of cans to foods producing serious health problems when they exceed allowable concentration limits for consumption. In this work, a method was assessed for the determination of BPA, BisDMA, and PA in vegetable food cans from Mexico using a food simulant. Those disruptors were determined by HPLC connected to an Evaporative Light Scattering Detector (ELSD), and simultaneous detection by UV-Vis detector was used for validation. The most frequently found disruptor in major concentration was PA over the range of 5.40 to 112.39 μg l−1. The samples analysed did not exceed the migration limit accepted by the US-FDA and US-EPA for bisphenols. Our results showed that HPLC-ELSD produces chromatograms with accurate signals and smaller detection limits than the UV-Vis detector for the substances analysed here.
Nitrogen doped carbon nanomaterials for biosensing applications
Get PDFTesis (Doctorado en Nanociencias y Nanotecnología)"The doping of carbon nanostructures with elements such as nitrogen and boron adds useful characteristics to the already remarkable features exhibited by nanocarbons. These new properties can be used for tackling several obstacles encountered for nanotechnology based applications, specially in biotechnology, where biocompatibility and sensitivity are crucial parameters for biosensing applications development. In this thesis work, we report the synthesis of nitrogendoped graphitic nanoribbons, along with their characterization by SEM and TEM. Raman and XPS spectroscopy results are also shown, and electrical characterization results are presented as well. Our results demonstrate how the presence of nitrogen produces novel morphologic, chemical and physical properties on graphitic nanoribbons, which in turn make the nanomaterial a promising candidate for bioelectronics research. Additionaly, we present results of theoretical and experimental research on interactions of doped carbon nanomaterials and biomolecules. Our theoretical findings suggest strong effects of doping on the stability of interactions between graphene and dopamine, whereas our experimental results suggest improved electrical properties for nitrogen-doped carbon nanotubes based biodevices when compared with undoped ones. This thesis shows, from theoretical and experimental studies, that doping of carbon nanostructures can be useful for sensing of biomolecules.
Reconfigurable dynamical logic gate with linear core
No full text"A dynamically reconfigurable linear core logic gate is a device that allows logical outputs dependent upon configurable parameters set within device. The device is comprised of three blocks: The first block receives at least one input signal and determines whether the signal o signals are low or high in comparison with a threshold reference signal. The second block sums the logic signals of the first block with an offset signal. The third block determines if the sum realized in the second block is a low or high by checking whether the sum falls within a predetermined interval.
Difference map and its electronic circuit realization
Get PDF"In this paper we study the dynamical behavior of the one-dimensional discrete-time system, the so-called iterated map. Namely, a bimodal quadratic map is introduced which is obtained as an amplification of the difference between well-known logistic and tent maps. Thus, it is denoted as the so-called difference map. The difference map exhibits a variety of behaviors according to the selection of the bifurcation parameter. The corresponding bifurcations are studied by numerical simulations and experimentally. The stability of the difference map is studied by means of Lyapunov exponent and is proved to be chaotic according to Devaney’s definition of chaos. Later on, a design of the electronic implementation of the difference map is presented. The difference map electronic circuit is built using operational amplifiers, resistors and an analog multiplier. It turns out that this electronic circuit presents fixed points, periodicity, chaos and intermittency that match with high accuracy to the corresponding values predicted theoretically.
Virtual estimator for piecewise linear systems based on observability analysis
Get PDF"This article proposes a virtual sensor for piecewise linear systems based on observability analysis that is in function of a commutation law related with the system's outpu. This virtual sensor is also known as a state estimator. Besides, it presents a detector of active mode when the commutation sequences of each linear subsystem are arbitrary and unknown. For the previous, this article proposes a set of virtual estimators that discern the commutation paths of the system and allow estimating their output. In this work a methodology in order to test the observability for piecewise linear systems with discrete time is proposed. An academic example is presented to show the obtained results.