Band-gap Shift In Cds Semiconductor By Photoacoustic Spectroscopy: Evidence Of A Cubic To Hexagonal Lattice Transition

The band-gap energies of the CdS semiconductor are obtained by a photoacoustic spectroscopy (PAS) technique over a range of temperature of thermal annealing (TTA), in which the evolution of the sample structure is characterized by x-ray diffraction patterns. The PAS experiment gives a set of data for the band-gap shift in the region of the fundamental absorption edge. With increasing TTA the band-gap shift increases up to a critical TTA when its slope decreases in a roughly symmetrical way. It is suggested that at this temperature a cubic to hexagonal-lattice transition occurs.64329129

Magneto--Acoustic Energetics Study of the Seismically Active Flare of 15 February 2011

Multi--wavelength studies of energetic solar flares with seismic emissions have revealed interesting common features between them. We studied the first GOES X--class flare of the 24th solar cycle, as detected by the Solar Dynamics Observatory (SDO). For context, seismic activity from this flare (SOL2011-02-15T01:55-X2.2, in NOAA AR 11158) has been reported in the literature (Kosovichev, 2011; Zharkov et al., 2011). Based on Dopplergram data from the Helioseismic and Magnetic Imager (HMI), we applied standard methods of local helioseismology in order to identify the seismic sources in this event. RHESSI hard X-ray data are used to check the correlation between the location of the seismic sources and the particle precipitation sites in during the flare. Using HMI magnetogram data, the temporal profile of fluctuations in the photospheric line-of-sight magnetic field is used to estimate the magnetic field change in the region where the seismic signal was observed. This leads to an estimate of the work done by the Lorentz-force transient on the photosphere of the source region. In this instance this is found to be a significant fraction of the acoustic energy in the attendant seismic emission, suggesting that Lorentz forces can contribute significantly to the generation of sunquakes. However, there are regions in which the signature of the Lorentz-force is much stronger, but from which no significant acoustic emission emanates.Comment: Submitted to Solar Physic

Study of encapsulation parameters to improve content of lycopene in tomato (Solanum lycopersicum L.) powders

The aim was to examine conditions of convective drying and spray-drying to improve preservation of lycopene content in tomatoes. The weight, size, colour, pH and °Brix values were evaluated in fresh fruit (FF) and colour (L, a, b), hue, and chrome indices were analysed from dried tomatoes, too. Tomato paste was dried (40, 50, 60, and 80 °C with times of 540, 390, 270, and 240 min) under convection conditions and pulverized. In the encapsulation treatments core material with tomato powders of 50, 60, and 70%, shell solution of maltodextrin/gum arabic 1:1, flow rate of 4, 6, 9, and 12 ml min–1, and inlet air T of 160, 170, and 180 °C were used. The physicochemical properties of FF corresponded to a degree of ripeness for consumption. The a, a/b, and hue values of dried tomatoes at 50 °C significantly correlated to red colouring and higher lycopene content (47.98±1.49 mg/100 g). The encapsulation with 50% and 60% of tomato powders, 170 °C and 9 ml min–1 treatments increased lycopene contents to 10.41 mg/100 g, 10.20 mg/100 g, and 11.51 mg/100 g, respectively. The results demonstrated that the physicochemical and functional properties were influenced by drying conditions, providing useful information for increasing the stability of lycopene in dried tomatoes

Optimization of the efficiency in an induction machine drive by algorithm based on the interior point method

[EN] This work optimizes the efficiency of the squirrel cage type Inverter-Induction Machine (IM) system, using an algorithm based on the Interior Point Method (IPM), where the input variables are the electromagnetic torque and the rotor speed at steady state,and as outputs the optimal efficiency and slip values are obtained. The optimum rotor flux value is calculated, which is used as a reference in the flux control loop, in the direct control vector method of the IM. Simulation results are obtained where the increase in efficiency is observed in low load states. The experimental installation used in the implementation of the vector control with maximum system efficiency is described, and the experimental results obtained are shown. A discussion is carried out on the results and the use of the Interior Point Optimization Method.[ES] En este trabajo se realiza la optimización de la eficiencia del sistema  Inversor-Máquina de Inducción (MI) del tipo jaula de ardilla, utilizando un algoritmo basado en el Método de Punto Interior (MPI), donde las variables de entrada son el par electromagnético y la velocidad del rotor en estado estacionario, y como salidas se obtienen los valores de la eficiencia óptima y del deslizamiento. Se calcula el valor del flujo óptimo del rotor que se utiliza como referencia en el lazo de control del flujo, en el control vectorial método directo de la MI. Se obtienen resultados de simulación donde se observa el incremento de la eficiencia en estados de baja carga. Se describe la instalación experimental usada en la implementación del control vectorial con máxima eficiencia del sistema, y se muestran los resultados experimentales obtenidos. 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