An array of lens-coupled antennas for cosmic microwave background measurements in the 30 Ghz band     

Angel Colin  David Ortiz  Enrique Villa  Edurado Artal  Enrique Martínez-González 《Experimental Astronomy》2012,33(1):27-37

An array of bow-tie slot antennas coupled through an extended hemispherical lens is proposed to operate in the 30?GHz frequency band. The design includes a combination of three microstrip Wilkinson power dividers (WPD) and transitions to coplanar wave guides (CPW) to form the feeding antenna network. This configuration is suitable for the integration with heterodyne imaging detectors commonly used in radioastronomy. Measurements and simulation results exhibit a frequency range of operation from 20 to 40?GHz with a bandwidth of 24% achieved for ?10?dB return loss at the central frequency. The measured radiation patterns show a maximum peak gain of around 13?dB with HPBW of 10° for the E-plane, and whose first side lobes are lower than 13?dB below the main lobe in both angular shift sides. The presented results will be considered as preliminary feasibility studies in the 30?GHz QUIJOTE-CMB Instrument, which is designed to study the anisotropies of the Cosmic Microwave Background (CMB).  相似文献   

Late Quaternary vegetation and climate dynamics in central-eastern Brazil: insights from a ~35k cal a bp peat record in the Cerrado biome     

Ingrid Horák-Terra  Antonio Martínez Cortizas  Cynthia Fernandes Pinto Da Luz  Alexandre Christófaro Silva  Tim Mighall  Plínio Barbosa De Camargo  Carlos Victor Mendonça-Filho  Paulo Eduardo De Oliveira  Francisco Willian Cruz  Pablo Vidal-Torrado 《第四纪科学杂志》2020,35(5):664-676

The late Quaternary evolution of central-eastern Brazil has been under-researched. Questions remain as to the origin of the Cerrado, a highly endangered biome, and other types of vegetation, such as the Capões – small vegetation islands of semi-deciduous and mountain forests. We investigated the factors that influenced the expansion and contraction of the Cerrado and Capões during the late Quaternary (last ~35 ka), using a multi-proxy approach: stable isotopes (δ¹³C, δ¹⁵N), geochemistry, pollen and multivariate statistics derived from a peat core (Pinheiro mire, Serra do Espinhaço Meridional). Five major shifts in precipitation, temperature, vegetation and landscape stability occurred at different timescales. Our study revealed that changes in the South Atlantic Convergence Zone (SACZ) seem to have been coeval with these shifts: from the Late Glacial Maximum to mid-Holocene the SACZ remained near (~29.6 to ~16.5k cal a bp ) and over (~16.5 to ~6.1 k cal a bp ) the study area, providing humidity to the region. This challenges previous research which suggested that climate was drier for this time period. At present, the Capões are likely to be a remnant of a more humid climate; meanwhile, the Cerrado biome seems to have stablished in the late Holocene, after ~3.1 k cal a bp .  相似文献   

Frasnian–Famennian crisis in the Malaguide Complex (Betic Cordillera,Spain)     

Rosario Rodríguez‐Cañero  Agustín Martín‐Algarra 《地学学报》2014,26(1):38-54

Devonian sediments of the Malaguide Complex potentially could include the Frasnian–Famennian boundary, one of the five greatest Phanerozoic biotic crises. Conodont biofacies and microfacies of carbonate clasts from a pebbly mudstone underlying Tournaisian radiolarites allows identification, for the first time in the Malaguide Complex, of Devonian shallow marine environments laterally grading to deeper realms. The clasts yielded Frasnian conodont associations of the falsiovalis to rhenana biozones, with six biofacies that reveal different environmental conditions in their source areas. Source sediments were dismantled and redeposited within the pebbly mudstone, whose origin is tentatively related to one of the events that are associated worldwide with the Frasnian–Famennian crisis. The latter is recorded, in two equivalent Malaguide pelagic successions, by stratigraphic discontinuities, and it was, probably, tectonically and/or eustatically controlled, as in other Alpine‐Mediterranean Paleotethyan margins.  相似文献   

Late Quaternary (Marine Isotope Stage 3 to Recent) sedimentary evolution of the Basque shelf (southern Bay of Biscay)     

Blanca Martínez‐García  Arantxa Bodego  Jone Mendicoa  Ana Pascual  Julio Rodríguez‐Lázaro 《Boreas: An International Journal of Quaternary Research》2014,43(4):973-988

Late Quaternary (MIS 3 to Recent) oceanographic evolution of the Basque shelf has been analysed for the first time based on the sedimentological analysis of three cores obtained from the middle and outer shelves. The cores are located in two interfluves separated by the San Sebastian canyon. The variability of the percentage of the planktonic foraminifera species Neogloboquadrina pachyderma sin. and of δ¹⁸O_bull allowed us to identify the influence of colder and warmer waters in the Basque shelf during the late Quaternary. From ～56 cal. ka BP to the end of the Last Glacial Maximum (19 cal. ka BP) the sedimentary record shows a decreasing trend in the mean grain size that correlates with the eustatic sea‐level fall. The last Deglaciation (19–11.5 cal. ka BP) is characterized by a sea‐level rise that produced an important hiatus in the western outer shelf. During the Holocene, the middle and outer shelves present different behaviours. From 11.5 to 6.7 cal. ka BP, in the outer shelf the sea‐level rise that started during the Deglaciation produced a hiatus, whereas in the middle shelf the sedimentary succession records the presence of warm to temperate waters. Between 6.7–4.9 cal. ka BP, the entrance of cold surface water‐masses that only affected the middle shelf has been identified, and temperate to warm waters occurred in the outer shelf. The cold surface water‐masses retreated during 4.9–4.3 cal. ka BP in the middle shelf. Finally, from 4.3 cal. ka BP to Recent, the middle shelf registers a hiatus due to sea‐level stabilization after a generalized transgression, synchronous to a decrease in the energy of the water‐masses in the outer shelf. In conclusion, the environmental changes detected in the Basque shelf are attributed to both regional and eustatic sea‐level changes.  相似文献   

Trends in the frequency of synoptic types in central-southern Chile in the period 1961–2012 using the Jenkinson and Collison synoptic classification     

Pablo?SarricoleaEmail authorView author&#;s OrcID profile  Oliver?Meseguer-Ruiz  Javier?Martín-Vide  Luis?Outeiro 《Theoretical and Applied Climatology》2018,134(1-2):193-204

Atmospheric circulation patterns in southern Chile (42° 30′ S) were studied in order to determine and analyse the most characteristic synoptic types and their recent trends, as well as to gain an understanding of how they are associated with low-frequency variability patterns. According to the Jenkinson and Collison (J&C) classification method, a 16-point grid of sea-level pressure data was employed. The findings reveal that some synoptic types show statistically significant trends with a 95% confidence level, positively for anticyclonic westerly hybrids (AW) and advective types for third and fourth quadrant wind flows (W, NW, and N) and negatively for SW and cyclonic hybrids (CS and CSW). A model has been constructed of the linear regression of some weather types with teleconnections that most affect Chile: the undetermined types (U), AW were associated with El Niño or the warm phase of the Pacific Decadal Oscillation (PDO), whereas the cyclonic northerly and cyclonic northeasterly types (CN and CNE) were associated with La Niña or cool phase of the PDO. The weather types associated with Antarctic Oscillation (AAO) in its positive phase are anticyclonic northerly and northeasterly and northerly advection types, while in its negative phase are cyclonic southwesterly and advection types.  相似文献   

Effects of a Fence on Pollutant Dispersion in a Boundary Layer Exposed to a Rural-to-Urban Transition     

H. E. Eisma  J. M. Tomas  M. J. B. M. Pourquie  G. E. Elsinga  H. J. J. Jonker  J. Westerweel 《Boundary-Layer Meteorology》2018,169(2):185-208

Simultaneous particle-image velocimetry and laser-induced fluorescence combined with large-eddy simulations are used to investigate the flow and pollutant dispersion behaviour in a rural-to-urban roughness transition. The urban roughness is characterized by an array of cubical obstacles in an aligned arrangement. A plane fence is added one obstacle height h upstream of the urban roughness elements, with three different fence heights considered. A smooth-wall turbulent boundary layer with a depth of 10h is used as the approaching flow, and a passive tracer is released from a uniform line source 1h upstream of the fence. A shear layer is formed at the top of the fence, which increases in strength for the higher fence cases, resulting in a deeper internal boundary layer (IBL). It is found that the mean flow for the rural-to-urban transition can be described by means of a mixing-length model provided that the transitional effects are accounted for. The mixing-length formulation for sparse urban canopies, as found in the literature, is extended to take into account the blockage effect in dense canopies. Additionally, the average mean concentration field is found to scale with the IBL depth and the bulk velocity in the IBL.  相似文献   

Pollutant Dispersion in Boundary Layers Exposed to Rural-to-Urban Transitions: Varying the Spanwise Length Scale of the Roughness     

J. M. Tomas  H. E. Eisma  M. J. B. M. Pourquie  G. E. Elsinga  H. J. J. Jonker  J. Westerweel 《Boundary-Layer Meteorology》2017,163(2):225-251

Both large-eddy simulations (LES) and water-tunnel experiments, using simultaneous stereoscopic particle image velocimetry and laser-induced fluorescence, have been used to investigate pollutant dispersion mechanisms in regions where the surface changes from rural to urban roughness. The urban roughness was characterized by an array of rectangular obstacles in an in-line arrangement. The streamwise length scale of the roughness was kept constant, while the spanwise length scale was varied by varying the obstacle aspect ratio l / h between 1 and 8, where l is the spanwise dimension of the obstacles and h is the height of the obstacles. Additionally, the case of two-dimensional roughness (riblets) was considered in LES. A smooth-wall turbulent boundary layer of depth 10h was used as the approaching flow, and a line source of passive tracer was placed 2h upstream of the urban canopy. The experimental and numerical results show good agreement, while minor discrepancies are readily explained. It is found that for \(l/h=2\) the drag induced by the urban canopy is largest of all considered cases, and is caused by a large-scale secondary flow. In addition, due to the roughness transition the vertical advective pollutant flux is the main ventilation mechanism in the first three streets. Furthermore, by means of linear stochastic estimation the mean flow structure is identified that is responsible for street-canyon ventilation for the sixth street and onwards. Moreover, it is shown that the vertical length scale of this structure increases with increasing aspect ratio of the obstacles in the canopy, while the streamwise length scale does not show a similar trend.  相似文献   

The influence of elevation on soil properties and forest litter in the Siliceous Moncayo Massif,SW Europe   总被引：1，自引：0，他引：1  

David Badía  Alberto Ruiz  Antonio Girona  Clara Martí  José Casanova  Paloma Ibarra  Raquel Zufiaurre 《山地科学学报》2016,13(12):2155-2169

Understanding the effects of elevation and related factors (climate, vegetation) on the physical and chemical soil properties can help to predict changes in response to future climate or afforestation forcings. This work aims to contribute to the knowledge of soil evolution and the classification of forest soils in relation to elevation in the montane stage, with special attention to podzolization and humus forms. The northern flank of the Moncayo Massif (Iberian Range, SW Europe) provides a unique opportunity to study a forest soils catena within a consistent quartzitic parent material over a relatively steep elevation gradient. With increasing elevation, pH, base saturation, exchangeable potassium, and fine silt-sized particles decrease significantly, while organic matter, the C/N ratio, soil aggregate stability, water repellency and coarse sand-sized particles increase significantly. The soil profiles shared a set of properties in all horizons: loamy-skeletal particle-size, extreme acidity (pH-H₂O<5.6) and low base saturation (<50%). The most prevalent soil forming processes in the catena include topsoil organic matter accumulation and even podzolization, which increases with elevation. From the upper to lower landscape positions of wooded montane stage of the Moncayo Massif, mull-moder-mor humus and an Umbrisol-Cambisol-Podzol soil unit sequences were found.  相似文献   

Origin and implications of mafic xenoliths associated with Cenozoic extension-related volcanism in the Válencia Trough, NE Spain     

Prof. E. -R. Neumann  Dr. J. Martí  Dr. J. Mitjavila  E. Wulff-Pedersen 《Mineralogy and Petrology》1999,65(1-2):113-139

Summary The Válencia Trough of northeastern Spain represents a poorly understood region of Cenozoic extension-related magmatism in western Europe. We present chemical data on mafic xenoliths and their host basalt from the Roca Negra cinder cone in the Catalán Volcanic Zone in the Válencia Trough. The xenoliths consist of augite+hornblende+ oxides±plagioclase±apatite±olivine::Lbiotitelorthopyroxene, and range from clinopyroxenites and hornblendites to gabbroic rocks. The major and trace element compositions of the xenoliths are compatible with formation as cumulates from a range of olivine tholeiitic to strongly alkaline magmas, and show a strong affinity to the Middle Miocene to Recent rift-related magmatism in the Cátalan Volcanic Zone. The xenoliths formed at temperatures of 1110–1180 °C, pressures of 2–7 kb (with 10 kb as the upper limit), and oxygen fugacities corresponding to 1–2 log units above the NNO oxygen buffer. The estimated pressure range implies formation in magma chambers within the crust, possibly also near the crust/mantle boundary (underplating). The presence of crustal cumulates indicates that the total volume of magmas emplaced into the crust in the Cátalan Volcanic Zone may be significantly larger than indicated by surface exposures. Isotopic compositions of the xenoliths are⁸⁷Sr/⁸⁶Sr: 0.703537–0.703647,¹⁴³Nd/¹⁴⁴Nd: 0.512732–0.512766,²⁰⁶Pb/²⁰⁴Pb: 18.097–19.106,²⁰⁷Pb/²⁰⁴Pb: 15.522–15.579, and²⁰⁸Pb/²⁰⁴Pb: 37.850–38.794. This range suggests the involvement of two mantle source components. One of these may be the low-velocity component recognized in Cenozoic magmatism in the eastern Atlantic Ocean to central Europe and western Mediterranean. The other component, which differs from those involved in other domains of Cenozoic volcanism in Europe and adjacent areas, may be located in the lithospheric mantle underlying NE Spain, which was metasomatized during late Variscan to early Alpine deformation.

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Herkunft und Bedeutung mafischer Xenolithe aus känozoiscben Extensions-bezogenen Vulkaniten aus dem Valencia Trog, Nordost-Spanien

Zusammenfassung Der Válencia Trog in Nordost-Spanien stellt eine noch wenig verstandene Region mit känozoischen Extensions-bezogenern Magmatismus in Westeuropa dar. Wir geben hier chemische Daten über mafische Xenolithe und ihre basaltischen Muttergesteine aus dem Roca Negra Kegei in der vulkanischen Zone von Catalan im Valencia Trog. Die Xenolithe bestehen aus Augit+Hornblende+Oxiden±Plagioklas±Apatit±Olivin±Biotit±Orthopyroxen und reichen in ihrer Zusammensetzung von Klinopyroxeniten und Homblenditen his zu gabbroischen Gesteinen. Die Haupt- und Spurenelementzusammensetzung der Xenolithe entspricht einer Kumulatbildung aus Olivin-tholéitischen bis stark alkalischen Magmen and zeigt eine deutliche Affinität mit dem mittelmiozanen bis rezenten Rift-bezogenen Magmatismus in der vulkanischen Zone von Catalan. Die Xenolithe bildeten sich bei Temperaturen von 1.110 bis 1.180 °C und bei Drucken von 2–7 kb (mit 10 kb als Obergrenze) und bei Sauerstoff-Fugazitäten, die 1 bis 2 log Einheiten über dem NNO Sauerstoff-Puffer liegen. Die abgeschätzten Drucke weisen auf Bildung in Magmakammern innerhalb der Kruste bin, womölich auch in der Nähe der Kruste-Mantelgrenze (Underplating). Das Vorkommen von krustalen Kumulaten zeigt, daß das gesamte Volumen von Magma, das in die Kruste der vulkanischen Zone von Catalan eingedrungen ist, wesentlich größer ist als das, das man aus Oberflächen-Ausbissen entnehmen k6nnte. Die Isotopen-Zusammensetzung der Xenolithe sind⁸⁷Sr/⁸⁶Sr: 0.703537–0.703647,¹⁴³Nd/¹⁴⁴Nd: 0.512732–0.512766,²⁰⁶Pb/204 Pb: 18.097–19.106,²⁰⁷Pb/²⁰⁴Pb: 15.522–15.579, and²⁰⁸Pb/²⁰⁴Pb: 37.850–38.794. Dies läßt erkennen, daß es sich bier um zwei verschiedene Mantel-Quellen handelt. Eine davon könnte die Niedrig-Geschwindigkeitskomponente sein, die man in känozoiscben Magmatiten des östlichen Atlantischen Ozeans, sowie in Zentraleuropa und im westlichen Mittelmeer erkannt hat. Die andere Komponete unterscheidet sich von jenen, die in anderen Bereichen von känozoischem Vulkanismus in Europa und benachbarten Gebieten vorkommen. Sie könnte im lithosphärischen Mantel unterhalb von Nordost-Spanien liegen, der während der variszischen bis zur frühalpidischen Deformation metasomatisch beeinflußt wurde.

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With 10 Figures  相似文献   

Structural and kinematic analysis of the Corredoiras detachment: evidence for early Variscan synconvergent extension in the Ordenes Complex, NW Spain   总被引：1，自引：1，他引：0  

F. Díaz García  J. R. Martínez Catalán  R. Arenas  P. González Cuadra 《International Journal of Earth Sciences》1999,88(2):337-351

 An important detachment is described in the allochthonous Ordenes Complex, in the NW Iberian Massif, and its meaning is related to the kinematics of contemporaneous convergent structures. The Corredoiras Detachment (CD) separates a hangingwall unit, characterised by a medium-pressure metamorphic gradient, from a footwall high-pressure and high-temperature unit and an underlying ophiolitic unit. An associated ductile shear zone, nearly 2000 m thick, developed in the lower part of the hangingwall unit, where the Corredoiras Orthogneiss, a Lower Ordovician metagranite, was progressively transformed into augengneisses, mylonitic and ultramylonitic gneisses. The attitude of the stretching and mineral lineation in the mylonites varies due to late refolding at map scale, but the sense of movement can be estimated, being roughly top to the SE. According to crosscutting relationships, the CD developed subsequent to the thrusting of the high-pressure/high-temperature unit onto the ophiolitic unit, and prior to younger extensional detachments, upright folding and strike-slip tectonics. The geometric relationships of the CD with the previous structures in the footwall unit, the subtractive character of the metamorphic gap between its hangingwall and footwall, and the available isotopic data suggest that the CD is an early Variscan, ductile extensional detachment, the movement of which was roughly simultaneous with the onset of thrusting of the allochthonous complexes over their relative autochthon. Received: 17 November 1998 / Accepted: 4 April 1999  相似文献