Infrared sensor-based temperature control for domestic induction cooktops

In this paper, a precise real-time temperature control system based on infrared (IR) thermometry for domestic induction cooking is presented. The temperature in the vessel constitutes the control variable of the closed-loop power control system implemented in a commercial induction cooker. A proportional-integral controller is applied to establish the output power level in order to reach the target temperature. An optical system and a signal conditioning circuit have been implemented. For the signal processing a microprocessor with 12-bit ADC and a sampling rate of 1 Ksps has been used. The analysis of the contributions to the infrared radiation permits the definition of a procedure to estimate the temperature of the vessel with a maximum temperature error of 5 °C in the range between 60 and 250 °C for a known cookware emissivity. A simple and necessary calibration procedure with a black-body sample is presented

Recent advances in the catalytic asymmetric 1,3-dipolar cycloaddition of azomethine ylides

Catalytic asymmetric 1,3-dipolar cycloadditions of azomethine ylides have turned out to be one of the most efficient methods for the preparation of enantioenriched pyrrolidines. The past decade has witnessed the development of a bunch of well-defined catalytic systems capable of affording excellent diastereo and enantioselectivities. Recently, a great effort has been focused on expanding the scope of the cycloaddition with regard to both reaction partners. In this review, we will discuss important advances that have been reported in this area since 2011The Ministerio de Economía y Competitividad (MINECO, project CTQ2012-3579) and Consejería de Educación de la Comunidad de Madrid (programme AVANCAT; S2009/PPQ-1634

First self-resonant frequency of power inductors based on approximated corrected stray capacitances

Inductive devices are extensively employed in power electronic systems due to their magnetic energy storage and power transfer capabilities. The current trend is towards increasing the frequency of operation in order to reduce the size of the magnetic components, but the main drawback is that the parasitic capacitance effect can become significant, and degrade the performance of the system. This work analyses the influence of this stray capacitance, and considers how to improve the performance of the device. In general, the impact of the stray capacitance on a magnetic component can be reduced by two methods: reducing the parasitic capacitance between turns of the winding or, alternatively, modifying the arrangement of the connection between turns. To evaluate the last option, an approximated expression of the first self-resonant frequency of the magnetic device is proposed. This gives a rapid assessment of the performance of different devices maintaining the overall equivalent inductance. The proposed expression accounts for the influence of the connection between turns in the bandwidth of the component. Finally, some numerical results are verified with planar coils manufactured on two-layer printed circuit boards

Dark solitons and vortices in PT-symmetric nonlinear media: from spontaneous symmetry breaking to nonlinear PT phase transitions

We consider nonlinear analogues of Parity-Time (PT) symmetric linear systems exhibiting defocusing nonlinearities. We study the ground state and excited states (dark solitons and vortices) of the system and report the following remarkable features. For relatively weak values of the parameter $\varepsilon$ controlling the strength of the PT-symmetric potential, excited states undergo (analytically tractable) spontaneous symmetry breaking; as $\varepsilon$ is further increased, the ground state and first excited state, as well as branches of higher multi-soliton (multi-vortex) states, collide in pairs and disappear in blue-sky bifurcations, in a way which is strongly reminiscent of the linear PT-phase transition ---thus termed the nonlinear PT-phase transition. Past this critical point, initialization of, e.g., the former ground state leads to spontaneously emerging solitons and vortices.Comment: 8 pages, 8 figure

Guiding chemical pulses through geometry: Y-junctions

We study computationally and experimentally the propagation of chemical pulses in complex geometries.The reaction of interest, CO oxidation, takes place on single crystal Pt(110) surfaces that are microlithographically patterned; they are also addressable through a focused laser beam, manipulated through galvanometer mirrors, capable of locally altering the crystal temperature and thus affecting pulse propagation. We focus on sudden changes in the domain shape (corners in a Y-junction geometry) that can affect the pulse dynamics; we also show how brief, localized temperature perturbations can be used to control reactive pulse propagation.The computational results are corroborated through experimental studies in which the pulses are visualized using Reflection Anisotropy Microscopy.Comment: submitted to Phys. Rev.

Pegmatitas en materiales metamórficos del norte de la provincia de Córdoba. Mineralogía y posibilidades económicas

[Resumen] En relación con rocas metamórficas de edad Precámbrica y metamorfismo de grado medio-alto se han estudiado más de 60 masas de pegmatitas cuarzo-feldespáticas compuestas por cuarzo, feldespato potásico, albita, moscovita, turma1 ina, granate, biotita, menas metálicas, minerales de uranio y otros. Las masas pegmatíticas son de formas irregulares o 1entejonares subconcordantes con la esquistosidad regional más manifiesta. Sus dimensiones oscilan entre unos decímetros y decenas de metros, y su continuidad lateral su pera en algunos casos los trescientos metros. Considerando sólo las masas de potencia métrica, por sus reservas, cal idad química de sus principales especies minerales, tamaño de grano, texturas, etc. es planteable la obtención industrial de cuarzo, feldespato potásico, feldespato sódico y moscovita[Abstract] More than 60 outcrops of quartz-fe1despatic pagmatites have been studied re1ated with Precambrian metamorphic rocks of medium-high grade. The pagmatites are composed of quartz, potash fe1dspar, a1bite, muscovite, turma1 ine, garnet, biotite, ores, uranium minerals and others. The pegmatite outcrops hare irregular o lenticular forms, subparallell to the main regional schistosity. They vary in size between a few decimeters to some tens of meters, whi1e su lateral continuity exceed in sorne cases 300 meterse By taking into account on1y the outcrop of metric size, their stocks, chemica1 qual ity of the main mineral species, grain size, texture, etc., it can be planned the industrial recovery of quartz, potash feldspar, sodic fe1dspar and muscovit