RF&MW - Grup de Recerca de Sistemes, Dispositius i Materials de RF i Microones
http://hdl.handle.net/2117/652
Fri, 09 Dec 2016 06:48:46 GMT2016-12-09T06:48:46ZWalking solitons
http://hdl.handle.net/2117/97891
Walking solitons
Torner Sabata, Lluís; Santos Blanco, M. Concepción; Mihalache, Dumitru; Mazilu, D; Crasovan, L C
By and large, optical
Wed, 07 Dec 2016 16:04:24 GMThttp://hdl.handle.net/2117/978912016-12-07T16:04:24ZTorner Sabata, LluísSantos Blanco, M. ConcepciónMihalache, DumitruMazilu, DCrasovan, L CBy and large, opticalSuperconductividad: historia y fundamentos
http://hdl.handle.net/2117/97788
Superconductividad: historia y fundamentos
O'Callaghan Castellà, Juan Manuel
Mon, 05 Dec 2016 15:22:40 GMThttp://hdl.handle.net/2117/977882016-12-05T15:22:40ZO'Callaghan Castellà, Juan ManuelCI de microondas. Aplicaciones y mercado
http://hdl.handle.net/2117/96449
CI de microondas. Aplicaciones y mercado
Artal, Eduardo; Comerón Tejero, Adolfo; Corbella Sanahuja, Ignasi
Wed, 09 Nov 2016 17:56:53 GMThttp://hdl.handle.net/2117/964492016-11-09T17:56:53ZArtal, EduardoComerón Tejero, AdolfoCorbella Sanahuja, IgnasiThe use of rapid prototyping techniques (RPT) to manufacture micro channels suitable for high operation pressures and uPIV
http://hdl.handle.net/2117/91433
The use of rapid prototyping techniques (RPT) to manufacture micro channels suitable for high operation pressures and uPIV
Farré Lladós, Josep; Casals Terré, Jasmina; Voltas Aguilar, Jordi; G. Westerberg, Lars
This paper aims to present a new methodology to manufacture micro-channels suitable for high operating pressures and micro particle image velocimetry (µPIV) measurements using a rapid-prototyping high-resolution 3D printer. This methodology can fabricate channels down to 250 µm and withstand pressures of up to 5 ± 0.2 MPa. The manufacturing times are much shorter than in soft lithography processes.
The novel manufacturing method developed takes advantage of the recently improved resolution in 3D printers to manufacture an rapid prototyping technique part that contains the hose connections and a micro-channel useful for microfluidics. A method to assemble one wall of the micro-channel using UV curable glue with a glass slide is presented – an operation required to prepare the channel for µPIV measurements. Once built, the micro-channel has been evaluated when working under pressure and the grease flow behavior in it has been measured using µPIV. Furthermore, the minimum achievable channels have been defined using a confocal microscopy study.
This technique is much faster than previous micro-manufacturing techniques where different steps were needed to obtain the micro-machined parts. However, due to current 3D printers ' resolutions (around 50 µm) and according to the experimental results, channels smaller than 250-µm2 cross-section should not be used to characterize fluid flow behaviors, as inaccuracies in the channel boundaries can deeply affect the fluid flow behavior.
The present methodology is developed due to the need to validate micro-channels using µPIV to lubricate critical components (bearings and gears) in wind turbines.
This novel micro-manufacturing technique overcomes current techniques, as it requires less manufacturing steps and therefore it is faster and with less associated costs to manufacture micro-channels down to 250-µm2 cross-section that can withstand pressures higher than 5 MPa that can be used to characterize microfluidic flow behavior using µPIV.
Thu, 03 Nov 2016 14:58:59 GMThttp://hdl.handle.net/2117/914332016-11-03T14:58:59ZFarré Lladós, JosepCasals Terré, JasminaVoltas Aguilar, JordiG. Westerberg, LarsThis paper aims to present a new methodology to manufacture micro-channels suitable for high operating pressures and micro particle image velocimetry (µPIV) measurements using a rapid-prototyping high-resolution 3D printer. This methodology can fabricate channels down to 250 µm and withstand pressures of up to 5 ± 0.2 MPa. The manufacturing times are much shorter than in soft lithography processes.
The novel manufacturing method developed takes advantage of the recently improved resolution in 3D printers to manufacture an rapid prototyping technique part that contains the hose connections and a micro-channel useful for microfluidics. A method to assemble one wall of the micro-channel using UV curable glue with a glass slide is presented – an operation required to prepare the channel for µPIV measurements. Once built, the micro-channel has been evaluated when working under pressure and the grease flow behavior in it has been measured using µPIV. Furthermore, the minimum achievable channels have been defined using a confocal microscopy study.
This technique is much faster than previous micro-manufacturing techniques where different steps were needed to obtain the micro-machined parts. However, due to current 3D printers ' resolutions (around 50 µm) and according to the experimental results, channels smaller than 250-µm2 cross-section should not be used to characterize fluid flow behaviors, as inaccuracies in the channel boundaries can deeply affect the fluid flow behavior.
The present methodology is developed due to the need to validate micro-channels using µPIV to lubricate critical components (bearings and gears) in wind turbines.
This novel micro-manufacturing technique overcomes current techniques, as it requires less manufacturing steps and therefore it is faster and with less associated costs to manufacture micro-channels down to 250-µm2 cross-section that can withstand pressures higher than 5 MPa that can be used to characterize microfluidic flow behavior using µPIV.SMOS instrument performance and calibration after six years in orbit
http://hdl.handle.net/2117/91134
SMOS instrument performance and calibration after six years in orbit
Martín Neira, Manuel; Oliva, Roger; Corbella Sanahuja, Ignasi; Duffo Ubeda, Núria; Durán Martínez, Israel; Torres Torres, Francisco; Kainulainen, Juha; Closa, Josep; Zurita Campos, Alberto Manuel; Cabot, François; Khazaal, Ali; Anterrieu, E.; Barbosa, José; Tenerelli, Joseph; Turiel, Antonio; Delwart, Steven
ESA's Soil Moisture and Ocean Salinity (SMOS) mission, launched 2-Nov-2009, has been in orbit for over 6 years, and its Microwave Imaging Radiometer with Aperture Synthesis (MIRAS) in two dimensions keeps working well. The calibration strategy remains overall as established after the commissioning phase, with a few improvements. The data for this whole period has been reprocessed with a new fully polarimetric version of the Level-1 processor which includes a refined calibration schema for the antenna losses. This reprocessing has allowed the assessment of an improved performance benchmark. An overview of the results and the progress achieved in both calibration and image reconstruction is presented in this contribution.
Wed, 26 Oct 2016 17:26:19 GMThttp://hdl.handle.net/2117/911342016-10-26T17:26:19ZMartín Neira, ManuelOliva, RogerCorbella Sanahuja, IgnasiDuffo Ubeda, NúriaDurán Martínez, IsraelTorres Torres, FranciscoKainulainen, JuhaClosa, JosepZurita Campos, Alberto ManuelCabot, FrançoisKhazaal, AliAnterrieu, E.Barbosa, JoséTenerelli, JosephTuriel, AntonioDelwart, StevenESA's Soil Moisture and Ocean Salinity (SMOS) mission, launched 2-Nov-2009, has been in orbit for over 6 years, and its Microwave Imaging Radiometer with Aperture Synthesis (MIRAS) in two dimensions keeps working well. The calibration strategy remains overall as established after the commissioning phase, with a few improvements. The data for this whole period has been reprocessed with a new fully polarimetric version of the Level-1 processor which includes a refined calibration schema for the antenna losses. This reprocessing has allowed the assessment of an improved performance benchmark. An overview of the results and the progress achieved in both calibration and image reconstruction is presented in this contribution.Nodal sampling: a new image reconstruction algorithm for SMOS
http://hdl.handle.net/2117/90880
Nodal sampling: a new image reconstruction algorithm for SMOS
Gonzalez Gambau, Verónica; Turiel, Antonio; Olmedo Casal, Estrella; Martinez, Justino; Corbella Sanahuja, Ignasi; Camps Carmona, Adriano José
Soil moisture and ocean salinity (SMOS) brightness temperature (TB) images and calibrated visibilities are related by the so-called G -matrix. Due to the incomplete sampling at some spatial frequencies, sharp transitions in the TB scenes generate a Gibbs-like contamination ringing and spread sidelobes. In the current SMOS image reconstruction strategy, a Blackman window is applied to the Fourier components of the TBs to diminish the amplitude of artifacts such as ripples, as well as other Gibbs -like effects. In this paper, a novel image reconstruction algorithm focused on the reduction of Gibbs -like contamination in TB images is proposed. It is based on sampling the TB images at the nodal points, that is, at those points at which the oscillating interference causes the minimum distortion to the geophysical signal. Results show a significant reduction of ripples and sidelobes in strongly radio-frequency interference contaminated images. This technique has been thoroughly validated using snapshots over the ocean, by comparing TBs reconstructed in the standard way or using the nodal sampling (NS) with modeled TBs. Tests have revealed that the standard deviation of the difference between the measurement and the model is reduced around 1 K over clean and stable zones when using NS technique with respect to the SMOS image reconstruction baseline. The reduction is approximately 0.7 K when considering the global ocean. This represents a crucial improvement in TB quality, which will translate in an enhancement of the retrieved geophysical parameters, particularly the sea surface salinity.
Wed, 19 Oct 2016 14:42:51 GMThttp://hdl.handle.net/2117/908802016-10-19T14:42:51ZGonzalez Gambau, VerónicaTuriel, AntonioOlmedo Casal, EstrellaMartinez, JustinoCorbella Sanahuja, IgnasiCamps Carmona, Adriano JoséSoil moisture and ocean salinity (SMOS) brightness temperature (TB) images and calibrated visibilities are related by the so-called G -matrix. Due to the incomplete sampling at some spatial frequencies, sharp transitions in the TB scenes generate a Gibbs-like contamination ringing and spread sidelobes. In the current SMOS image reconstruction strategy, a Blackman window is applied to the Fourier components of the TBs to diminish the amplitude of artifacts such as ripples, as well as other Gibbs -like effects. In this paper, a novel image reconstruction algorithm focused on the reduction of Gibbs -like contamination in TB images is proposed. It is based on sampling the TB images at the nodal points, that is, at those points at which the oscillating interference causes the minimum distortion to the geophysical signal. Results show a significant reduction of ripples and sidelobes in strongly radio-frequency interference contaminated images. This technique has been thoroughly validated using snapshots over the ocean, by comparing TBs reconstructed in the standard way or using the nodal sampling (NS) with modeled TBs. Tests have revealed that the standard deviation of the difference between the measurement and the model is reduced around 1 K over clean and stable zones when using NS technique with respect to the SMOS image reconstruction baseline. The reduction is approximately 0.7 K when considering the global ocean. This represents a crucial improvement in TB quality, which will translate in an enhancement of the retrieved geophysical parameters, particularly the sea surface salinity.Scattering and emissivity of rain events using boundary element method
http://hdl.handle.net/2117/89163
Scattering and emissivity of rain events using boundary element method
Duffo Ubeda, Núria; Vall-Llossera Ferran, Mercedes Magdalena; Camps Carmona, Adriano José; Corbella Sanahuja, Ignasi; Bará Temes, Francisco Javier; Torres Torres, Francisco
The theory of thermal microwave emission from a bounded medium containing random nonspherical discrete scatters is studied. It is known that for a medium of constant temperature the emissivities can be related to the bistatic scattering coefficients. Such relations hold for the four Stokes parameters. The down-welling polarimetric emission of the rain can be computed by means of the radiative transfer equation, which contains the four Stokes parameters. In order to apply the above equation to a realistic rain event, raindrop shapes have to be taken into account in the computation of the scattering amplitudes. Those shapes were obtained by Pruppacher and Pitter and are quite different from a sphere when the size increases. In this paper a procedure based in the Boundary Element Method (B.E.M.) is presented to compute the scattering amplitudes for each drop shape. Results are then averaged for all drop radii with a weighting function given by the Laws-Parson law. This law establishes the relationship between the drop size distribution and the rain intensity. A Gaussian distribution of the drop canting angle due to the wind has been also considered. Finally, some numerical results are presented. The scenario consists of a rain cell of 4 Km height at a uniform temperature, considering the wind effect. The values of the rain intensity and wind speed and direction have been obtained from realistic measurements recorded by a meteorological station located in campus. In order to validate these results, the four Stokes parameters obtained with these simulations were compared with the ones measured by a X-band polarimetric radiometer developed in our laboratory.
Mon, 25 Jul 2016 12:40:49 GMThttp://hdl.handle.net/2117/891632016-07-25T12:40:49ZDuffo Ubeda, NúriaVall-Llossera Ferran, Mercedes MagdalenaCamps Carmona, Adriano JoséCorbella Sanahuja, IgnasiBará Temes, Francisco JavierTorres Torres, FranciscoThe theory of thermal microwave emission from a bounded medium containing random nonspherical discrete scatters is studied. It is known that for a medium of constant temperature the emissivities can be related to the bistatic scattering coefficients. Such relations hold for the four Stokes parameters. The down-welling polarimetric emission of the rain can be computed by means of the radiative transfer equation, which contains the four Stokes parameters. In order to apply the above equation to a realistic rain event, raindrop shapes have to be taken into account in the computation of the scattering amplitudes. Those shapes were obtained by Pruppacher and Pitter and are quite different from a sphere when the size increases. In this paper a procedure based in the Boundary Element Method (B.E.M.) is presented to compute the scattering amplitudes for each drop shape. Results are then averaged for all drop radii with a weighting function given by the Laws-Parson law. This law establishes the relationship between the drop size distribution and the rain intensity. A Gaussian distribution of the drop canting angle due to the wind has been also considered. Finally, some numerical results are presented. The scenario consists of a rain cell of 4 Km height at a uniform temperature, considering the wind effect. The values of the rain intensity and wind speed and direction have been obtained from realistic measurements recorded by a meteorological station located in campus. In order to validate these results, the four Stokes parameters obtained with these simulations were compared with the ones measured by a X-band polarimetric radiometer developed in our laboratory.Modelo de transistores MESFET en régimen no lineal
http://hdl.handle.net/2117/88876
Modelo de transistores MESFET en régimen no lineal
Corbella Sanahuja, Ignasi; Legido, Jm; Pradell i Cara, Lluís
Tue, 19 Jul 2016 07:29:03 GMThttp://hdl.handle.net/2117/888762016-07-19T07:29:03ZCorbella Sanahuja, IgnasiLegido, JmPradell i Cara, LluísMethod of moments applied to the analysis of rough surfaces modelled by fractals
http://hdl.handle.net/2117/88555
Method of moments applied to the analysis of rough surfaces modelled by fractals
Vall-Llossera Ferran, Mercedes Magdalena; Duffo Ubeda, Núria; Camps Carmona, Adriano José; Corbella Sanahuja, Ignasi; Bará Temes, Francisco Javier; Torres Torres, Francisco
The Scattering and Emissivity of rough surfaces involve solutions to non-linear differential equations. Different approaches have been used in the literature to obtain approximate solutions under some hypothesis. For example Kirchhoff solution is used when the roughness is gentle on the scale of the wavelength.
In this paper the Method of Moments is used to analyze the scattering of arbitrary surfaces. No approximation about the scale roughness is necessary. Both Gaussian and Fractal surfaces have been modeled and compared. The introduction of fractal geometry provides a new tool to describe natural rough surfaces. A first inside to the properties and parameters that describe fractal geometry has been done in order to characterize them statistically. It has been demonstrated that geometrical and scattering characteristics are controlled by Fractal descriptors, including fractal dimension.
As a first step, our simulations refer to a (topological) one-dimensional (1-D) profile embedded in a two-dimensional (2-D) space. Physically, this corresponds to assume that both the electromagnetic field and the surface height are constant along a fixed direction. Extension to the case of a 2-D surface embedded in a three-dimensional (3-D) space is not conceptually difficult, but any simulation run requires a much longer computational time. Furthermore, scattering results obtained for 1-D profiles give also a good indication of scattering dependence on 2-D surface parameters.
Wed, 06 Jul 2016 13:26:55 GMThttp://hdl.handle.net/2117/885552016-07-06T13:26:55ZVall-Llossera Ferran, Mercedes MagdalenaDuffo Ubeda, NúriaCamps Carmona, Adriano JoséCorbella Sanahuja, IgnasiBará Temes, Francisco JavierTorres Torres, FranciscoThe Scattering and Emissivity of rough surfaces involve solutions to non-linear differential equations. Different approaches have been used in the literature to obtain approximate solutions under some hypothesis. For example Kirchhoff solution is used when the roughness is gentle on the scale of the wavelength.
In this paper the Method of Moments is used to analyze the scattering of arbitrary surfaces. No approximation about the scale roughness is necessary. Both Gaussian and Fractal surfaces have been modeled and compared. The introduction of fractal geometry provides a new tool to describe natural rough surfaces. A first inside to the properties and parameters that describe fractal geometry has been done in order to characterize them statistically. It has been demonstrated that geometrical and scattering characteristics are controlled by Fractal descriptors, including fractal dimension.
As a first step, our simulations refer to a (topological) one-dimensional (1-D) profile embedded in a two-dimensional (2-D) space. Physically, this corresponds to assume that both the electromagnetic field and the surface height are constant along a fixed direction. Extension to the case of a 2-D surface embedded in a three-dimensional (3-D) space is not conceptually difficult, but any simulation run requires a much longer computational time. Furthermore, scattering results obtained for 1-D profiles give also a good indication of scattering dependence on 2-D surface parameters.Evaluation of MIRAS space borne instrument performance: snap shot radiometric accuracy and its improvement by means of pixel averaging
http://hdl.handle.net/2117/88554
Evaluation of MIRAS space borne instrument performance: snap shot radiometric accuracy and its improvement by means of pixel averaging
Camps Carmona, Adriano José; Torres Torres, Francisco; Bará Temes, Francisco Javier; Corbella Sanahuja, Ignasi; Martín Neira, Manuel
Wed, 06 Jul 2016 13:19:37 GMThttp://hdl.handle.net/2117/885542016-07-06T13:19:37ZCamps Carmona, Adriano JoséTorres Torres, FranciscoBará Temes, Francisco JavierCorbella Sanahuja, IgnasiMartín Neira, Manuel