Composition and luminescence of AlInGaN layers grown by plasma-assisted molecular beam epitaxy

A study of AlInGaN epilayers, grown by plasma-assisted molecular beam epitaxy, was performed using spatially resolved x-ray microanalysis and luminescence spectroscopy in order to investigate competition between the incorporation of In, Al, and Ga as a function of the growth temperature in the 565-660 °C range and the nominal AlN mole fraction. The samples studied have AlN and InN mole fractions in the ranges of 4%-30% and 0%-16%, respectively. Composition measurements show the effect of decreasing temperature to be an increase in the incorporation of InN, accompanied by a small but discernible decrease in the ratio of GaN to AlN mole fractions. The incorporation of In is also shown to be significantly increased by decreasing the Al mole fraction. Optical emission peaks, observed by cathodoluminescence mapping and by photoluminescence, provide further information on the epilayer compositions as a function of substrate temperature, and the dependencies of peak energy and linewidth are plotted

FORMULATION OF THE HEAT CONDUCTION EQUATION FOR HETEROGENEOUS MEDIA WITH MULTIPLE SPATIAL SCALES USING REITERATED HOMOGENIZATION

Heterogeneous media with multiple spatial scales are finding increased importance in engineering. An example might be a large scale, otherwise homogeneous medium filled with dispersed small-scale particles that form aggregate structures at an intermediate scale. The objective in this paper is to formulate the strong-form Fourier heat conduction equation for such media using the method of reiterated homogenization. The phases are assumed to have a perfect thermal contact at the interface. The ratio of two successive length scales of the medium is a constant small parameter ε. The method is an up-scaling procedure that writes the temperature field as an asymptotic multiple-scale expansion in powers of the small parameter ε . The technique leads to two pairs of local and homogenized equations, linked by effective coefficients. In this manner the medium behavior at the smallest scales is seen to affect the macroscale behavior, which is the main interest in engineering. To facilitate the physical understanding of the formulation, an analytical solution is obtained for the heat conduction equation in a functionally graded material (FGM). The approach presented here may serve as a basis for future efforts to numerically compute effective properties of heterogeneous media with multiple spatial scales

Design and experimental verification of ridge gap waveguide in bed of nails for parallel-plate mode suppression

This study describes the design and experimental verification of the ridge gap waveguide, appearing in the gap between parallel metal plates. One of the plates has a texture in the form of a wave-guiding metal ridge surrounded by metal posts. The latter posts, referred to as a pin surface or bed of nails, are designed to give a stopband for the normal parallel-plate modes between 10 and 23 GHz. The hardware demonstrator includes two 90° bends and two capacitive coupled coaxial transitions enabling measurements with a vector network analyser (VNA). The measured results verify the large bandwidth and low losses of the quasi-transverse electromagnetic (TEM) mode propagating along the guiding ridge, and that 90° bends can be designed in the same way as for microstrip lines. The demonstrator is designed for use around 15 GHz. Still, the ridge gap waveguide is more advantageous for frequencies above 30 GHz, because it can be realised entirely from metal using milling or moulding, and there are no requirements for conducting joints between the two plates that otherwise is a problem when realising conventional hollow waveguides. © 2011 The Institution of Engineering and Technology.Kildal, P.; Zaman, AU.; Rajo Iglesias, E.; Alfonso Alós, E.; Valero-Nogueira, A. (2011). Design and experimental verification of ridge gap waveguide in bed of nails for parallel-plate mode suppression. IET Microwaves Antennas and Propagation. 5(3):262-270. doi:10.1049/iet-map.2010.0089S26227053Kildal, P.-S., Alfonso, E., Valero-Nogueira, A., & Rajo-Iglesias, E. (2009). Local Metamaterial-Based Waveguides in Gaps Between Parallel Metal Plates. IEEE Antennas and Wireless Propagation Letters, 8, 84-87. doi:10.1109/lawp.2008.2011147Kildal, P.-S.: ‘Waveguides and transmission lines in gaps between parallel conducting surfaces’, (European Patent Application EP08159791.6)7 July 2008Rajo-Iglesias, E., Zaman, A. U., & Kildal, P.-S. (2010). Parallel Plate Cavity Mode Suppression in Microstrip Circuit Packages Using a Lid of Nails. IEEE Microwave and Wireless Components Letters, 20(1), 31-33. doi:10.1109/lmwc.2009.2035960Kildal, P.-S. (1990). Artificially soft and hard surfaces in electromagnetics. IEEE Transactions on Antennas and Propagation, 38(10), 1537-1544. doi:10.1109/8.59765Valero-Nogueira, A., Alfonso, E., Herranz, J. I., & Kildal, P.-S. (2009). Experimental Demonstration of Local Quasi-TEM Gap Modes in Single-Hard-Wall Waveguides. IEEE Microwave and Wireless Components Letters, 19(9), 536-538. doi:10.1109/lmwc.2009.2027051Lier, E. (1990). Analysis of soft and hard strip-loaded horns using a circular cylindrical model. IEEE Transactions on Antennas and Propagation, 38(6), 783-793. doi:10.1109/8.55573Sievenpiper, D., Lijun Zhang, Broas, R. F. J., Alexopolous, N. G., & Yablonovitch, E. (1999). High-impedance electromagnetic surfaces with a forbidden frequency band. IEEE Transactions on Microwave Theory and Techniques, 47(11), 2059-2074. doi:10.1109/22.798001Silveirinha, M. G., Fernandes, C. A., & Costa, J. R. (2008). Electromagnetic Characterization of Textured Surfaces Formed by Metallic Pins. IEEE Transactions on Antennas and Propagation, 56(2), 405-415. doi:10.1109/tap.2007.915442Lindell, I. V. (2000). Ideal boundary and generalised soft and hard conditions. IEE Proceedings - Microwaves, Antennas and Propagation, 147(6), 495. doi:10.1049/ip-map:20000827Valero-Nogueira, A., Alfonso, E., Herranz, J. I., & Baquero, M. (2007). Planar slot-array antenna fed by an oversized quasi-TEM waveguide. Microwave and Optical Technology Letters, 49(8), 1875-1877. doi:10.1002/mop.22586Šipuš, Z., Merkel, H., & Kildal, P.-S. (1997). Green’s functions for planar soft and hard surfaces derived by asymptotic boundary conditions. IEE Proceedings - Microwaves, Antennas and Propagation, 144(5), 321. doi:10.1049/ip-map:19971335CST Microwave Studio 2008. Available at: www.cst.comKehn, M. N. M., & Kildal, P.-S. (2005). Miniaturized rectangular hard waveguides for use in multifrequency phased arrays. IEEE Transactions on Antennas and Propagation, 53(1), 100-109. doi:10.1109/tap.2004.840519Malcolm Ng Mou Kehn, M. N. M., Nannetti, Cucini, Maci, & Kildal. (2006). Analysis of dispersion in dipole-FSS loaded hard rectangular waveguide. IEEE Transactions on Antennas and Propagation, 54(12), 2275-2282. doi:10.1109/tap.2006.879198Grbic, A., & Eleftheriades, G. V. (2003). Periodic analysis of a 2-D negative refractive index transmission line structure. IEEE Transactions on Antennas and Propagation, 51(10), 2604-2611. doi:10.1109/tap.2003.817543Eleftheriades, G.V., and Balmain, K.G.: ‘Metamaterials for controlling and guiding electromagnetic radiation’, (US Patent 6859114 – Filed 2 June 2003)McKinzie, W.F.: ‘Circuit and method for suppression of electromagnetic coupling and switching noise in multilayer printed circuit boards’, (US Patent No. 7,215,007 B2)Schellenberg, J. M. (1995). CAD models for suspended and inverted microstrip. IEEE Transactions on Microwave Theory and Techniques, 43(6), 1247-1252. doi:10.1109/22.390179Anderson, T. N. (1956). Rectangular and Ridge Waveguide. IEEE Transactions on Microwave Theory and Techniques, 4(4), 201-209. doi:10.1109/tmtt.1956.1125063Pozar, D.: ‘Microwave engineering’, 3rd(Wiley 2005), p. 139Bosiljevac, M., Sipus, Z., & Kildal, P.-S. (2010). Construction of Green’s functions of parallel plates with periodic texture with application to gap waveguides – a plane-wave spectral-domain approach. IET Microwaves, Antennas & Propagation, 4(11), 1799. doi:10.1049/iet-map.2009.0399Zaman, A. U., Rajo-Iglesias, E., Alfonso, E., & Kildal, P.-S. (2009). Design of transition from coaxial line to ridge gap waveguide. 2009 IEEE Antennas and Propagation Society International Symposium. doi:10.1109/aps.2009.5172186Sharp, E. D. (1963). A High-Power Wide-Band Waffle-Iron Filter. IEEE Transactions on Microwave Theory and Techniques, 11(2), 111-116. doi:10.1109/tmtt.1963.1125611KIRINO, H., OGAWA, K., & OHNO, T. (2008). A Variable Phase Shifter Using a Movable Waffle Iron Metal Plate and Its Applications to Phased Array Antennas. IEICE Transactions on Communications, E91-B(6), 1773-1782. doi:10.1093/ietcom/e91-b.6.177

Assessment of satellite-derived shorelines automatically extracted from Sentinel-2 imagery using SAET

The definition of the shoreline position from satellite imagery is of great interest among coastal monitoring techniques. Understanding the reality mapped by the resulting shorelines and defining their accuracy is of paramount importance. The assessment described in this paper constitutes a validation of the shorelines obtained by using the novel tool SAET (Shoreline Analysis and Extraction Tool) for automatic shoreline extraction. The resulting shorelines applying the different parameters available in SAET are assessed in 9 test sites with diverse morphology and oceanographic conditions along the Atlantic European and Western Mediterranean coasts. The reference data is obtained along large coastal segments (covering up to about 240 km) from nearly coincident very high-resolution satellite images. Different image processing levels and extraction methods have been tested, showing their key role in the accuracy of shoreline position. When defining the approximate shoreline position the Automated Water Extraction Index for images without shadows (AWEInsh) with a 0 threshold generally constitutes the best segmentation method. In turn, the employment of the mathematical morphological operations of dilation or erosion considerably improves the results in certain coastal typologies. On the contrary, the employment of atmospherically-corrected images has a smaller influence on the accuracy of the SDSs. Results support the idea that the magnitude of the errors is strongly related to the specific coastal conditions- In general, the lowest errors appear in low-energetic microtidal sites, contrary to the energetic and mesotidal coasts with gentle slopes. The shoreline errors range between 3.7 m and 13.5 m RMSE (root-mean-square error) among the different coastal types when selecting the most appropriate extraction parameters. The shoreline position identified with SAET shows a similar or better accuracy to that obtained by other tools

Incidencia del género en los niveles de actividad física en las clases de educación física

The main objective of this paper is to describe physical activity levels in physical education classes among primary schoolchildren and to observe differences between genders. For these purposes 42 students were selected (22 boys and 20 girls) (10,5 ± 0,8 years of age; 40,5 ± 8,3 kg of mass; 143,8 ± 7,1 cm of heigth; 19,4 ± 3,2 kg/m2 of BMI). Their level of physical activity was assessed using a GT3X accelerometer (Actigraph, Pensacola, FL, USA) carried during five school days, attached at the right hip, with an epoch of 1s. Intensity was determined by cut-offs proposed by Evenson et al. (2008). The results show that students do moderate to vigorous intensity around 17% and 13% for boys and girls respectively. No significant differences were observed.El objetivo principal de este trabajo, es describir los niveles de actividad física en clases de Educación Física con escolares de Educación Primaria y, observar las posibles diferencias según el género. Se seleccionaron 42 estudiantes (22 chicos y 20 chicas) (10,5 ± 0,8 años de edad; 40,5 ± 8,3 kg de masa; 143,8 ± 7,1 cm de altura; 19,4 ± 3,2 kg/m2 de IMC) 4 y se evaluó el nivel de actividad física a través del acelerómetro GT3X (Actigraph, Pensacola, FL, USA) llevado durante los cinco días de la jornada escolar, en la cadera derecha, con un epoch de 1s. La intensidad de la actividad física se determinó mediante los puntos de corte de Evenson et al. (2008). Los resultados muestran que los alumnos realizan actividad física a intensidad moderada y vigorosa en torno a 17% y 13% para chicos y chicas respectivamente, no observándose diferencias significativas estadísticamente

Elastic scattering with weakly bound projectiles

Possible effects of the break-up channel on the elastic scattering threshold anomaly has been investigated. We used the weakly bound 6,7Li nuclei, which is known to undergo break-up, as projectiles in order to study the elastic scattering on a 27Al target. In this contribution we present preliminary results of these experiments, which were analyzed in terms of the Optical Model and compared with other elastic scattering data using weakly bound nuclei as projectile. © 2007 American Institute of Physics.Fil:Figueira, J.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Fernández Niello, J.O. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Arazi, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Capurro, O.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Martí, G.V. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Pacheco, A.J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina