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Coupled Mode (coupled + mode)
Selected AbstractsBackward-wave directional coupler with complete coupling and broadband using conventional microstrip and 1D mushroom structureMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2006Jae-Gon Lee Abstract A new type of backward-wave coupled-line directional coupler with complete coupling and broadband, which is composed of a conventional microstrip and a 1D mushroom structure, is proposed. The 1D mushroom structure is employed for a double negative (DNG) transmission line. The coupler exhibits unusual characteristics such as complex propagation. The complex propagation constant of the coupled mode enables strong coupling due to exponential field decay. The performance of the proposed coupler is verified by c- and ,-mode analysis, full-wave simulation, and measurement. The measured coupling level of ,0.5 dB with 3-dB fractional bandwidth of 35% and high directivity of 30 dB is achieved. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1293,1296, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21622 [source] Single crystal X-ray study of the modulated structure in Ga2XTe3 with the defect zinc-blende structurePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2009S. Kashida Abstract Ga2Te3 crystallizes into the zinc-blende structure, where one third of the cation sites is vacant. Single crystal X-ray diffraction studies on quenched and annealed Ga2Te3 and CuGaTe2 crystals are reported. The obtained diffraction maps show, other than the zinc-blende type main reflections, satellite reflections at q1,1/17[110]c in quenched Ga2Te3 crystals and q2,1/20[210]c in annealed Ga2Te3 crystals, where the subscript c means the cubic sub-lattice. The analysis of the satellite reflections shows that the modulation is two dimensional, and is ascribed to a coupled mode of the amplitude type modulation caused by Ga vacancies and the displacive modulation of surrounding Te atoms, which has the polarization vector along the <001>c direction. The nature of the atomic modulations is discussed and the origin of the modulation is ascribed to Jahn-Teller type distortions around Ga vacancies. The experiments done on CuGaTe2 crystals indicate that the cation disorder compound sphalerite type CuGaTe2 contain the same modulated structure as Ga2Te3 crystals, but the cation ordered compound chalcopyrite type CuGaTe2 does not show the modulation. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A self-sustaining climate mode in the tropical atlantic, 1995,97: Observations and modellingTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 564 2000Itsuki C. Handoh Abstract An anomalous climatic event in the tropical Atlantic, starting in autumn 1995 and continuing into the autumn of 1997, is investigated. Using remotely sensed datasets and a reduced-gravity model, it is shown that this event contained both a warm and a cold phase, each of roughly 12 months duration. The propagating signal within each phase is identified in the sea surface height and temperature signatures as both equatorial and off-equatorial waves in the ocean, with coupling to atmospheric convection. The strength, geographical pattern and timing of the anomalous period is consistent with it being the first observed example of a coupled mode of interaction between the ocean and atmosphere found in two previous coupled ocean-atmosphere models of the tropics. This interpretation means that the two-phased climate event, which we will call the Equatorial Atlantic Oscillation (EAO), was associated with purely internal atmospheric and oceanographic variability within the Atlantic basin and hence was independent of the Pacific climate. It can also be inferred, from long-term monthly sea surface temperature and sea-level pressure datasets, that there were potentially several previous EAO events during the past century. [source] Atmospheric large-scale dynamics during the 2004/2005 winter drought in portugalINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 5 2007J. Santos Abstract The unusually dry conditions during the 2004/2005 winter in Portugal led to the development of an extreme/severe drought episode throughout the country with major socioeconomic impacts. In fact, at some locations, this winter was the driest in at least the last 60 years. A K-means classification of days into a set of five weather regimes (WRs), relevant for winter precipitation in Portugal, reveals a large prevalence of the two driest weather regimes during the 2004/2005 winter. These two regimes are basically linked to either anticyclonic circulation or easterly winds over Portugal and their prevalence explains the significant precipitation deficit. Winter precipitation variability in Portugal is indeed skillfully represented by linear models where the predictors are the frequencies of occurrence (FO) of these weather regimes. The dominance of the ,dry phases' of the main coupled modes between winter precipitation in Portugal and the large-scale atmospheric circulation also supports the prevalence of the dry regimes and the corresponding lack of precipitation. The predominance of the dry regimes can be explained by a remarkably strong enhancement of the climate-mean North Atlantic ridge, manifested by dynamically coherent anomalies in the geopotential heights, vorticity and temperature fields over the North Atlantic. The persistence of a warm-core asymmetrical eddy over the North Atlantic, with a nearly barotropic equivalent structure, is a manifestation of this large-scale anomaly. The blocking of the westerlies and the consequent northward shift in the axis of maximum moisture transports over the North Atlantic was one of the most striking changes in the large-scale atmospheric flow. Consequently, the main track of the developing baroclinic disturbances was sufficiently distant from Portugal to hamper the development of rain-generating conditions. As these dynamical conditions are common to other reportedly dry winters, they effectively constitute a key factor for the occurrence of a precipitation deficit in Portugal. Copyright © 2006 Royal Meteorological Society [source] Ultrafast dynamics of plasmon-phonon coupling: Estimation of electron mobility in GaAsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008*Article first published online: 29 NOV 200, Muneaki Hase Abstract Utilizing a femtosecond pump-probe technique, ultrafast relaxation of plasmon-like LO phonon-plasmon coupled (LOPC) modes is studied. The time-resolved reflectivity change exhibits strong mode beating between the LO phonon and the lower branch of the LOPC modes. It is revealed that the decay of the upper branch (or plasmon-like mode) of the coupled modes is very rapid in time-frequency space, explored by using wavelet analysis. The decay time of the plasmon-like LOPC mode, which corresponds to the relaxation time ,, is obtained to be , 79 fs and this time constant enables us to extract the electron mobility , to be 2074 ± 200 cm2/Vs. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Lamb Wave Interactions with Non-symmetric Features at Structural BoundariesPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2008M. R. Mofakhami The paper initially describes on a numerical basis how a Lamb wave would have to perform that has been initiated in a pure mode (either symmetric or anti,symmetric) and what the wave would have to anticipate in terms of mode conversion when being reflected at a surface not perpendicular to its traveling direction. The effects of changing in geometric specifications of non,symmetric artificial features like angle of sloping edge or partially sloping edges are studied. The results obtained from these studies are presented as the reflected and converted parts of the incident wave versus angle of the edge or percentage of the sloped edge. It has been further shown that Lamb waves being generated experimentally by a finite size transducer into a plate like structure thus most likely result in a combination of modes. Reflection of these combined modes at structural boundaries will therefore generate an even more complex coupling of modes. This situation is further aggravated if the structural boundary is not purely perpendicular to the traveling wave but has a slightly varying angle such as it might have to be anticipated at a countersunk rivet, a notch or even more extreme a crack in a metallic component. However from understanding the background of Lamb wave generation, mode separation and superposition, a systematic approach can be established that allows complex Lamb waves, such as they are observed when monitoring true structures, to be interpreted and understood. This approach has been explained on the basis of numerical result obtained from finite element analyses first before proving the findings by some fundamental experiments performed with variable angle beam transducers which demonstrates the difficulties in de,coupling Lamb wave modes and how to handle those coupled modes in terms of structural condition monitoring. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||