Articoli di riviste: "Vertical active coupler"

1

Fan, Guofang, Bing Han, Yuan Li, Hongyu Li, Ruitong Liu e Yongsheng Zhao. "A vertical coupler for InP active components". Optics & Laser Technology 95 (ottobre 2017): 14–17. http://dx.doi.org/10.1016/j.optlastec.2017.04.010.

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Zhang, Ruiying, Z. Ren, O. Ansell e S. Yu. "Flexible Coupling Ratio in Single Ring Resonator Through Active Vertical Coupler". IEEE Photonics Technology Letters 20, n. 13 (luglio 2008): 1202–4. http://dx.doi.org/10.1109/lpt.2008.925486.

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3

Liu, Can, Gongyuan Zhao, Fan Yang, Qiaoyin Lu e Weihua Guo. "Design of Compact but Fabrication-Tolerant Vertical Coupler for Active–Passive Integration". Journal of Lightwave Technology 36, n. 3 (1 febbraio 2018): 755–62. http://dx.doi.org/10.1109/jlt.2017.2771362.

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4

Thakulsukanant, K., e S. Yu. "Hybrid multicast mode based on active vertical coupler optical crosspoint switch matrix". Electronics Letters 43, n. 21 (2007): 1160. http://dx.doi.org/10.1049/el:20071303.

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5

Thakulsukanant, K., J. S. Van der Merwe, Z. Wang e S. Yu. "Serial-mode optical multicast based on active vertical coupler optical crosspoint switch matrix". Electronics Letters 43, n. 6 (2007): 361. http://dx.doi.org/10.1049/el:20073613.

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6

Varrazza, R., I. B. Djordjevic e S. Yu. "Active Vertical-Coupler-Based Optical Crosspoint Switch Matrix for Optical Packet-Switching Applications". Journal of Lightwave Technology 22, n. 9 (settembre 2004): 2034–42. http://dx.doi.org/10.1109/jlt.2004.833259.

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7

Siyuan Yu, Sheng-Chyan Lee, O. Ansell e R. Varrazza. "Lossless optical packet multicast using active vertical coupler based optical crosspoint switch matrix". Journal of Lightwave Technology 23, n. 10 (ottobre 2005): 2984–92. http://dx.doi.org/10.1109/jlt.2005.856170.

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8

Zhuoran Wang, N. Chi e Siyuan Yu. "2-to-4 optical multicast using active vertical coupler optical crosspoint switch matrix". IEEE Photonics Technology Letters 18, n. 1 (gennaio 2006): 286–88. http://dx.doi.org/10.1109/lpt.2005.862010.

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9

Lee, Chee-Wei. "A Review of Polarization Dependence Applications for Asymmetric Waveguides Vertical Couplers in Compound Semiconductor Indium Phosphide". International Journal of Optics 2011 (2011): 1–11. http://dx.doi.org/10.1155/2011/164023.

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This paper reviews and presents a coherent approach to the design of compact vertical coupler (VC) in InP-based compound semiconductor with variable polarization dependence. As a polarization-independent (PI) coupler, the VC is shown to transfer light with more than 90% efficiency for both transverse-electric (TE) and transverse-magnetic (TM) polarizations. As a polarization-mode splitter (PMS), the VC is shown to preferentially couple TE or TM modes with a contrast ratio of up to 20 dB. We further demonstrate the single-mesa VC, which simplifies the fabrication process and potentially could improve the process yield, and its integration with a multimode interferometer (MMI). The versatility makes the VC a compact and useful input-stage device that not only maximizes input/output coupling efficiency to small active devices but also provides a degree of polarization control before the actual device.

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Lin, Fang-Zheng, Yi-jen Chiu, Shun-An Tsai e Tsu-Hsiu Wu. "Laterally tapered undercut active waveguide fabricated by simple wet etching method for vertical waveguide directional coupler". Optics Express 16, n. 11 (12 maggio 2008): 7588. http://dx.doi.org/10.1364/oe.16.007588.

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11

Geldenhuys, R., J. S. van der Merwe, K. Thakulsukanant, Z. Wang, N. Chi e S. Yu. "Contention resolution and variable length optical packet switching using the active vertical-coupler-based optical Crosspoint switch". Optical Switching and Networking 8, n. 2 (aprile 2011): 86–92. http://dx.doi.org/10.1016/j.osn.2010.10.001.

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12

Chi, Nan. "Time-slot interchange using an optical buffer with a large variable delay range based on an active-vertical-coupler crosspoint switch". Optical Engineering 45, n. 10 (1 ottobre 2006): 105003. http://dx.doi.org/10.1117/1.2360178.

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13

Yufeng, Shao, Zhang Junwen, Fang Wuliang, Huang Bo e Chi Nan. "A flexible optical packet compression and routing scheme by using an active vertical coupler-based optical crosspoint switch matrix [Topics in Optical Communications". IEEE Communications Magazine 48, n. 8 (agosto 2010): 146–51. http://dx.doi.org/10.1109/mcom.2010.5534600.

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14

Zhuoran Wang, Nan Chi e Siyuan Yu. "Characterization of 1/spl times/N broadcast and 2/spl times/N multicast packet switching using active-vertical-coupler-based optical crosspoint switch". Journal of Lightwave Technology 24, n. 8 (agosto 2006): 2978–85. http://dx.doi.org/10.1109/jlt.2006.878062.

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15

López, Óscar García, Daniel Lasaosa, Manuel López-Amo e Marko Galarza. "Highly-efficient fully resonant vertical couplers for InP active-passive monolithic integration using vertically phase matched waveguides". Optics Express 21, n. 19 (19 settembre 2013): 22717. http://dx.doi.org/10.1364/oe.21.022717.

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16

Ventrice, Michael J., Christopher D. Thorncroft e Carl J. Schreck. "Impacts of Convectively Coupled Kelvin Waves on Environmental Conditions for Atlantic Tropical Cyclogenesis". Monthly Weather Review 140, n. 7 (1 luglio 2012): 2198–214. http://dx.doi.org/10.1175/mwr-d-11-00305.1.

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Abstract High-amplitude convectively coupled equatorial atmospheric Kelvin waves (CCKWs) are explored over the tropical Atlantic during the boreal summer (1989–2009). Focus is given to the atmospheric environmental conditions that are important for tropical cyclogenesis. CCKWs are characterized by deep westerly vertical wind shear to the east of its convectively active phase and easterly vertical wind shear to the west of it. This dynamical signature increases vertical wind shear over the western tropical Atlantic ahead of the convectively active phase, and reduces vertical wind shear after its passage. The opposite is true over the eastern tropical Atlantic where the climatological vertical wind shear is easterly. Positive total column water vapor (TCWV) anomalies progress eastward with the convectively active phase of the CCKW, whereas negative TCWV anomalies progress eastward with the convectively suppressed phase. During the passage of the convectively active phase of the CCKW, a zonally oriented strip of low-level cyclonic relative vorticity is generated over the tropical Atlantic. Two days later, this strip becomes more wavelike and moves back toward the west. This signature resembles a train of westward-moving easterly waves and suggests CCKWs may influence such events. Strong CCKWs over the tropical Atlantic tend to occur during the decay of the active convection associated with the Madden–Julian oscillation over the Pacific. This relationship could be used to provide better long-range forecasts of tropical convective patterns and Atlantic tropical cyclogenesis.

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17

Ma, Xiyue, Kean Chen e Jian Xu. "Active Control of Sound Transmission through Orthogonally Rib Stiffened Double-Panel Structure: Mechanism Analysis". Applied Sciences 9, n. 16 (10 agosto 2019): 3286. http://dx.doi.org/10.3390/app9163286.

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Physical mechanisms of active control of sound transmission through orthogonally two ribs stiffened double-panel structure are investigated. This is the continued work of the single rib stiffened case. For the orthogonally two ribs stiffened case, four different cluster mode groups can be coupled with each other, due to the interlaced coupling effects of the horizontal and vertical ribs. One cavity mode can couple with and transmit sound energy to any type of base plate mode of the radiating ribbed plate. Consequently, the main differences of the control mechanism, when compared with the single ribbed case, lie in two aspects. One is that a novel mechanism appears. That is, suppressing and rearranging the cavity modes simultaneously achieves the suppression of the base plate modes. The other is that rearrangement of the cavity modes to rearrange the base plate modes for achieving sound radiation cancellation almost does not appear. The reason is that all types of cavity mode can couple with any one of the base plate modes due to the coupling effects of the two ribs. There is only a need to rearrange several important cavity modes to achieve suppressing the base plate mode of the radiating ribbed plate.

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18

Chen, Jiayang, Hao Zhang, Junjie Jin, Jian Lin, Long Zhao, Zhuanfang Bi, Anping Huang e Zhisong Xiao. "Miniaturized optical gyroscope using active three-dimensional vertically coupled resonators". Optical Engineering 54, n. 10 (15 ottobre 2015): 107106. http://dx.doi.org/10.1117/1.oe.54.10.107106.

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19

Djordjev, K., Seung-June Choi, Sang-Jun Choi e P. D. Dapkus. "Vertically coupled InP microdisk switching devices with electroabsorptive active regions". IEEE Photonics Technology Letters 14, n. 8 (agosto 2002): 1115–17. http://dx.doi.org/10.1109/lpt.2002.1021987.

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20

Sheng-Chyan Lee, R. Varrazza e Siyuan Yu. "Advanced optical packet switching functions using active vertical-couplers-based optical switch matrix". IEEE Journal of Selected Topics in Quantum Electronics 12, n. 4 (luglio 2006): 817–27. http://dx.doi.org/10.1109/jstqe.2006.876176.

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21

Chyng Wen Tee, K. A. Williams, R. V. Penty e I. H. White. "Fabrication-tolerant active-passive integration scheme for vertically coupled microring resonator". IEEE Journal of Selected Topics in Quantum Electronics 12, n. 1 (gennaio 2006): 108–16. http://dx.doi.org/10.1109/jstqe.2005.862947.

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22

Galarza, Marko, Dries Van Thourhout, Roel Baets e Manuel Lopez-Amo. "Compact and highly-efficient polarization independent vertical resonant couplers for active-passive monolithic integration". Optics Express 16, n. 12 (23 maggio 2008): 8350. http://dx.doi.org/10.1364/oe.16.008350.

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23

Levitt, J. A., e N. G. Zorka. "The Influence of Tire Damping in Quarter Car Active Suspension Models". Journal of Dynamic Systems, Measurement, and Control 113, n. 1 (1 marzo 1991): 134–37. http://dx.doi.org/10.1115/1.2896339.

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Setting tire damping to zero when modeling automotive active suspension systems compels the misleading conclusions that, at the wheelhop frequency, no matter what forces are exerted between sprung and unsprung masses, their motion are uncoupled, and the vertical acceleration of the sprung mass will be unaffected. Alternatively, taking tire damping to be small but nonzero, the motions of the sprung and unsprung masses are coupled at all frequencies, and control forces can be used to reduce the sprung mass vertical acceleration at the wheelhop frequency. The effect of introducing tire damping can be quite large. In the case of a force law chosen to enhance ride along a straight smooth road, where road holding is not a major concern, setting the tire damping ratio to 0.02 reduces rms body acceleration by 30 percent.

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Choi, S. J., Z. Peng, Q. Yang, S. J. Choi e P. D. Dapkus. "An Eight-Channel Demultiplexing Switch Array Using Vertically Coupled Active Semiconductor Microdisk Resonators". IEEE Photonics Technology Letters 16, n. 11 (novembre 2004): 2517–19. http://dx.doi.org/10.1109/lpt.2004.835617.

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25

Chen, Jian Guo, Xia Feng e Xiao Ling Zhang. "A Vibration Attenuation Control Algorithm of Half Vehicle Using Active Suspension". Applied Mechanics and Materials 456 (ottobre 2013): 14–17. http://dx.doi.org/10.4028/www.scientific.net/amm.456.14.

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Vehicle suspension is a MIMO coupling nonlinear system; its vibration couples that of the tires. For the suspension without decoupling, the vibration attenuation is difficult to be controlled precisely. In order to attenuate the vibration of the vehicle effectively, a nonlinear half vehicle model with active suspension is established and a differential geometry approach is used to decouple the nonlinear suspension system. The decoupled system becomes independent linear subsystems, though pole assignment, the vibration attenuation of the sprung mass is achieved. The simulations show that the vertical and the pitching motion of the sprung mass are attenuated greatly, which indicates that the control algorithm is effective.

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26

Tenzer, Robert, e Ali Fadil. "Tectonic classification of vertical crustal motions – a case study for New Zealand". Contributions to Geophysics and Geodesy 46, n. 2 (1 giugno 2016): 91–109. http://dx.doi.org/10.1515/congeo-2016-0007.

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Abstract We investigate the relationship between vertical crustal motion and tectonic block configuration. The study is conducted along the active tectonic margin between the Australian and Pacific tectonic plates in New Zealand with a well-defined tectonic block configuration. For this purpose, the rates of vertical crustal motions relative to the ITRF2008 reference frame are estimated based on processing the GPS data (provided by the GeoNET project) collected at 123 continuous and semi-continuous GPS sites. The numerical results confirmed the uplift of the central Southern Alps at the current rate of 4.5 mm/yr. This tectonic uplift is coupled in the South Island by the subsidence on both sides of the Southern Alps. The detected rates of subsidence in the eastern South Island are typically less than 1 mm/yr. The subsidence in the Buller Region (in the northwest South Island) is 1.4–1.5 mm/yr. Except for the Taupo Volcanic Zone and the upper Raukumara Block (in the central and northeast North Island), the subsidence is prevailing in the North Island. The systematic subsidence up to 9 mm/yr is detected along the Dextral Fault Belt (in the lower North Island). The largest localized vertical displacements (between −10 and 17 mm/yr) in the Taupo Volcanic Zone are attributed to active tectonics, volcanisms and geothermal processes in this region. A classification of these vertical tectonic motions with respect to the tectonic block configuration reveals that most of tectonic blocks are systematically uplifted, subsided or tilted, except for regions characterized by a complex pattern of vertical motions attributed to active geothermal and volcanic processes.

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27

Dias, Juliana, e Olivier Pauluis. "Impacts of Convective Lifetime on Moist Geostrophic Adjustment". Journal of the Atmospheric Sciences 67, n. 9 (1 settembre 2010): 2960–71. http://dx.doi.org/10.1175/2010jas3405.1.

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Abstract This paper presents a theoretical study of the effects of moist convection on geostrophic adjustment in an infinite channel. The governing equations correspond to a linearized shallow water system of equations for the atmosphere first vertical baroclinic mode, which is coupled to a vertically averaged moisture equation. The coupling is through a parameterization that represents precipitation. The transient behavior and final state of the flow initially at rest with active precipitation limited to half of the channel is investigated, both numerically and analytically. It is shown that an initial imbalance resulting from precipitation induces a circulation that dries out the nonprecipitating region and further enhances precipitation. This interaction between precipitation and dynamics leads to a sharper temperature gradient and stronger jet in the final state, when compared to the dry adjustment. Unlike in the dry case, the moist geostrophic adjustment cannot be entirely determined from the initial unbalanced flow, since it depends on the time scale for convection. Analytic approximations are derived in limits of both fast and slow convective adjustment time.

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28

Hsing, J. Y., T. E. Tzeng, T. S. Lay e M. H. Shih. "Vertically coupled double-microdisk lasers composed of InGaAs quantum dots-in-a-well active layers". Journal of Applied Physics 121, n. 20 (28 maggio 2017): 203107. http://dx.doi.org/10.1063/1.4984273.

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Simpson, C. C., J. J. Sharples e J. P. Evans. "Resolving vorticity-driven lateral fire spread using the WRF-Fire coupled atmosphere–fire numerical model". Natural Hazards and Earth System Sciences 14, n. 9 (5 settembre 2014): 2359–71. http://dx.doi.org/10.5194/nhess-14-2359-2014.

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Abstract. Vorticity-driven lateral fire spread (VLS) is a form of dynamic fire behaviour, during which a wildland fire spreads rapidly across a steep leeward slope in a direction approximately transverse to the background winds. VLS is often accompanied by a downwind extension of the active flaming region and intense pyro-convection. In this study, the WRF-Fire (WRF stands for Weather Research and Forecasting) coupled atmosphere–fire model is used to examine the sensitivity of resolving VLS to both the horizontal and vertical grid spacing, and the fire-to-atmosphere coupling from within the model framework. The atmospheric horizontal and vertical grid spacing are varied between 25 and 90 m, and the fire-to-atmosphere coupling is either enabled or disabled. At high spatial resolutions, the inclusion of fire-to-atmosphere coupling increases the upslope and lateral rate of spread by factors of up to 2.7 and 9.5, respectively. This increase in the upslope and lateral rate of spread diminishes at coarser spatial resolutions, and VLS is not modelled for a horizontal and vertical grid spacing of 90 m. The lateral fire spread is driven by fire whirls formed due to an interaction between the background winds and the vertical circulation generated at the flank of the fire front as part of the pyro-convective updraft. The laterally advancing fire fronts become the dominant contributors to the extreme pyro-convection. The results presented in this study demonstrate that both high spatial resolution and two-way atmosphere–fire coupling are required to model VLS with WRF-Fire.

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Gennaretti, Massimo, Federico Porcacchia, Simone Migliore e Jacopo Serafini. "Assessment of Helicopter Pilot-in-the-Loop Models". International Journal of Aerospace Engineering 2017 (2017): 1–14. http://dx.doi.org/10.1155/2017/7849461.

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The aim of this paper is the evaluation of several pilot models found in the literature, suited for helicopter pilot-assisted and pilot-induced oscillations analyses. Three main topics are discussed: (i) sensitivity of rotorcraft-pilot couplings simulations on the application of the different pilot models available in the literature; (ii) effect of vehicle modeling on active pilot modeling; (iii) effects of interactions between active and passive pilot models. The focus is on hovering flight, where a specific adverse rotorcraft-pilot coupling phenomenon, the vertical bounce, may occur. Pilot models are coupled with a comprehensive aeroservoelastic model of a mid-weight helicopter. The numerical investigations are performed in frequency domain, in terms of eigenanalysis and frequency response analysis.

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31

Zhang, Jiang-Yong, Li-E. Cai, Bao-Ping Zhang, Shui-Qing Li, Feng Lin, Jing-Zhi Shang, Du-Xiang Wang, Ke-Chuang Lin, Jin-Zhong Yu e Qi-Ming Wang. "Low threshold lasing of GaN-based vertical cavity surface emitting lasers with an asymmetric coupled quantum well active region". Applied Physics Letters 93, n. 19 (10 novembre 2008): 191118. http://dx.doi.org/10.1063/1.3030876.

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Phocas, Marios C., e Kristis Alexandrou. "On decoding the structural behaviour of hybrid cable bending-active units in fastening, prestress and load-bearing state". International Journal of Space Structures 33, n. 2 (giugno 2018): 98–111. http://dx.doi.org/10.1177/0266351118795338.

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This article examines the structural behaviour of six structural units composed of single, simply paired and paired-interconnected bending-active members, coupled with a single cable element. The form-found curvilinear shape of the members is achieved through fastening by contracting auxiliary elements, as well as through further deformation by decreasing the cable’s length. The overall structural behaviour of the units is investigated based on a step-by-step finite-element analysis. All units are evaluated with regard to the components’ stresses and deformations developed during the form-finding process and subsequent external vertical loading, for different possible section thickness values of the elastic members.

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Roundy, Paul E. "Analysis of Convectively Coupled Kelvin Waves in the Indian Ocean MJO". Journal of the Atmospheric Sciences 65, n. 4 (1 aprile 2008): 1342–59. http://dx.doi.org/10.1175/2007jas2345.1.

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Abstract The active convective phase of the Madden–Julian oscillation (hereafter active MJO) comprises enhanced moist deep convection on its own temporal and spatial scales as well as increased variance in convection associated with higher-frequency modes. Synoptic-scale cloud superclusters apparently associated with convectively coupled Kelvin waves occur within the active convective envelopes of most MJO events. These convectively coupled Kelvin waves also occur during the suppressed convective phase of the MJO (hereafter suppressed MJO). This observational study presents an analysis of outgoing longwave radiation and reanalysis data to determine how these waves behave differently as they propagate through the active and suppressed MJO. Time indices of the MJO and Kelvin waves are derived for over the equatorial Indian Ocean. Dates of local extrema in these indices are used to composite data to discern how the waves and associated circulations behave on average; then, further composites are made based on subsets of this list of dates that are consistent with the two MJO phases. Results show that the MJO phase modulates the intensity of moist deep convection associated with the Kelvin waves, the evolution of the vertical structure of cloudiness linked to Kelvin waves, and patterns of upper-level outflow from convection coupled to Kelvin waves. Composites reveal that synoptic-scale circulations associated with the release of latent heat in convection coupled to Kelvin waves amplify and are left behind the waves in preferred geographical regions. The MJO modulates the amplitudes of these circulations and the locations where they get left behind the waves. Previous results have suggested a sharp distinction between the phase speeds of the MJO (4–8 m s−1) and of convectively coupled Kelvin waves (specifically 17 m s−1). In contrast, the present work suggests that convectively coupled Kelvin waves have a broad range of characteristic phase speeds, extending from 10 to 17 m s−1, depending on both the region of the world and the phase of the MJO through which they propagate.

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Wang, Qunsheng, Jing Zeng, Yi Wu e Bin Zhu. "Study on semi-active suspension applied on carbody underneath suspended system of high-speed railway vehicle". Journal of Vibration and Control 26, n. 9-10 (8 gennaio 2020): 671–79. http://dx.doi.org/10.1177/1077546319889863.

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Considering the coupling vibration of a flexible carbody and the underneath suspended equipment, a vertical coupled vibration model of a high-speed train was constructed. A roller test rig was conducted to validate the theoretical model. To reduce carbody elastic vibration, the semi-active vibration reduction models based on the Sky-hook and the linear quadratic regulator control strategies were proposed. The semi-active suspension system was installed between the carbody and the suspended equipment, and the influence of the semi-active suspension on carbody vibration reduction was analyzed. The results show that the semi-active suspension can significantly reduce carbody vibration, especially at high operating speeds. The higher the elastic vibration of carbody, the better the vibration reduction effect of the semi-active suspension. Compared with the passive suspension and the semi-active suspension, the semi-active suspension of the Sky-hook control has a relatively wider vibration control range, and has an obvious effect on carbody rigid and elastic vibration reduction. Although the semi-active suspension of the linear quadratic regulator control had little influence on the rigid carbody vibration, it could reduce most of the elastic carbody vibration.

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Ventrice, Michael J., e Chris D. Thorncroft. "The Role of Convectively Coupled Atmospheric Kelvin Waves on African Easterly Wave Activity". Monthly Weather Review 141, n. 6 (1 giugno 2013): 1910–24. http://dx.doi.org/10.1175/mwr-d-12-00147.1.

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Abstract The role of convectively coupled atmospheric Kelvin waves (CCKWs) on African easterly wave (AEW) activity is explored over tropical Africa during boreal summer. Examination of the pre-Alberto AEW in 2000 highlights the observation that the convective trigger for the initiation of the AEW was generated by a strong CCKW and that the subsequent intensification of the AEW at the West African coast was associated with a second CCKW. Composite analysis shows that, generally, AEW activity increases during and after the passage of the convectively active phase of strong CCKWs. The increase in AEW activity is consistent with convective triggering at the leading edge of the convective phase of the CCKW. This convective triggering occurs in a region where the background low-level easterly vertical wind shear is increased by the CCKW. As the AEW propagates westward through the convectively active phase of the CCKW, it can develop in an environment favorable for convection. It is also shown that this phase of the CCKW is characterized by enhanced meridional vorticity gradients in the core of the African easterly jet suggesting that enhanced mixed barotropic–baroclinic growth may also be responsible for enhanced AEW activity there.

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Sailer, Eleonora, David M. G. Taborda, Lidija Zdravkovic e David M. Potts. "Assessing the impact of vertical heat exchangers on the response of a retaining wall". E3S Web of Conferences 92 (2019): 16001. http://dx.doi.org/10.1051/e3sconf/20199216001.

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Shallow geothermal energy systems, e.g. borehole heat exchangers or thermo-active structures, provide sustainable space heating and cooling by exchanging heat with the ground. When installed within densely built urban environments, the thermo-hydro-mechanical (THM) interactions occurring due to changes in ground temperature, such as soil deformation and development of excess pore water pressures, may affect the mechanical behaviour of adjacent underground structures. This paper investigates the effects of vertical heat exchangers installed near a deep basement by performing fully coupled THM finite element analyses using the Imperial College Finite Element Program. Different heat exchanger configurations are considered and their influence on the response of the basement wall is assessed in two-dimensional plane strain analyses, where different methods of modelling the heat sources in this type of analysis are employed to evaluate their effect on the temperature field and the non-isothermal soil response.

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Fleischer, A. S., U. Troppenz, M. Hamacher e W. John. "Thermal analysis of bond layer influence on performance of an all-active vertically coupled, microring resonating laser". Microelectronics Reliability 46, n. 2-4 (febbraio 2006): 421–31. http://dx.doi.org/10.1016/j.microrel.2005.04.010.

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Hinkel, Kenneth M., Samuel I. Outcalt e Alan E. Taylor. "Seasonal patterns of coupled flow in the active layer at three sites in northwest North America". Canadian Journal of Earth Sciences 34, n. 5 (1 maggio 1997): 667–78. http://dx.doi.org/10.1139/e17-053.

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Vertical arrays of temperature and electric-potential probes were installed in the upper soil at sites along the Mackenzie River valley and on the North Slope of Alaska. Time series were obtained at subdiurnal frequencies throughout the year in the active layer and upper permafrost. If the data acquisition system is properly configured, the time series can be used to infer soil physiochemical processes. The electric potential develops primarily in response to soil water solute concentration gradients in the soil column, and is a crude surrogate of the soil water electrolytic conductivity. Summer precipitation can cause rapid penetration of the thaw front when percolating rainwater, warmed at the ground surface, carries sensible heat downward to the thawing front. Rates of warming at depth occur significantly faster than those typical of conductive heat transfer. In early winter, as the freezing front penetrates downward toward the permafrost table, ions are excluded from the ice and concentrated in the intermediate unfrozen zone. Nearly instantaneous warming of the active layer is triggered by spring snowmelt. At Happy Valley in northern Alaska, temperatures at the 29 cm depth rise from −7 to −3 °C in 1 h. For several hours during this event, the temperature at 29 cm is warmer than that at regions both above and below, producing a strong thermal inversion. Time series of electric potential, or a surrogate derived from electric potential, suggest rapid transport of meltwater from the snowpack to depth, probably through soil cracks. Serial events hasten active-layer warming by 1–2 weeks.

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Wang, Binrui, Yixuan Liu, Zhongwen Li, Dijian Chen, Ruizi Ma e Ling Wang. "Parallel Spine Design and CPG Motion Test of Quadruped Robot". International Journal of Pattern Recognition and Artificial Intelligence 34, n. 05 (26 agosto 2019): 2059013. http://dx.doi.org/10.1142/s0218001420590132.

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The spine of mammals aids in the stability of locomotion. Central Pattern Generators (CPGs) located in spinal cord can rapidly provide a rhythmic output signal during loss of sensory feedback on the basis of a simulated quadruped agent. In this paper, active spine of quadruped robot is shown to be extremely effective in motion. An active spine model based on the Parallel Kinematic Mechanism (PKM) system and biological phenomena is described. The general principles involved in constructing a neural network coupled with limbs and spine to solve specific problems are discussed. A CPG mathematical model based on Hopf nonlinear oscillators produces rhythmic signal during locomotion is described, where many parameters to be solved must be formulated in terms of desired stability, often subject to vertical stability analysis. Our simulations demonstrate that active spine with setting reasonable CPG parameters can reduce unnecessary lateral displacement during trot gait, improving the stability of quadruped robot. In addition, we demonstrate that physical prototype mechanism provides a framework which shows correctness of simulation, and stability can thus be easily embodied within locomotion.

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40

Jha, Basant K., Gabriel Samaila e Peter B. Malgwi. "Adomian decomposition method for combined effect of Hall and ion-slip on mixed convection flow of chemically reacting Newtonian fluid in a microchannel with heat absorption/generation". International Journal of Modern Physics C 31, n. 10 (9 settembre 2020): 2050150. http://dx.doi.org/10.1142/s0129183120501508.

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In this work, theoretical analysis is carried out on fully developed hydromagnetic flow of heat generating/absorbing fluid in a vertical microchannel in the presence of Hall and ion-slip effects. The governing coupled flow equations are obtained in dimensional form and thereafter simplified by employing some similarity transformation variables and quantities. The transformed coupled equations are solved by adopting the Adomian Decomposition Method (ADM) and their solution represented in closed form. Interesting influences of some active parameter on different flow features are shown using line graphs and Table. The numerical values for the results obtained in this work using ADM were validated with results obtained from existing benchmark. Results from the analysis reveal that in the existence of heat generation/absorption, the primary velocity and the temperature distribution could be enhanced by growing the ion-slip and Hall current parameter, whereas its influence on velocity is contrary along the secondary direction.

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41

Kamieniecki, Jan A., Maarten H. P. Ambaum, Robert S. Plant e Steven J. Woolnough. "The Implications of an Idealized Large-Scale Circulation for Mechanical Work Done by Tropical Convection". Journal of the Atmospheric Sciences 75, n. 8 (13 luglio 2018): 2533–47. http://dx.doi.org/10.1175/jas-d-17-0314.1.

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Abstract A thermodynamic analysis is presented of an overturning circulation simulated by two cloud-resolving models, coupled by a weak temperature gradient parameterization. Taken together, they represent two separated regions over different sea surface temperatures, and the coupling represents an idealized large-scale circulation such as the Walker circulation. It is demonstrated that a thermodynamic budget linking net heat input to the generation of mechanical energy can be partitioned into contributions from the large-scale interaction between the two regions, as represented by the weak temperature gradient approximation, and from convective motions in the active warm region and the suppressed cool region. Model results imply that such thermodynamic diagnostics for the aggregate system are barely affected by the strength of the coupling, even its introduction, or by the SST contrast between the regions. This indicates that the weak temperature gradient parameterization does not introduce anomalous thermodynamic behavior. We find that the vertical kinetic energy associated with the large-scale circulation is more than three orders of magnitude smaller than the typical vertical kinetic energy in each region. However, even with very weak coupling circulations, the contrast between the thermodynamic budget terms for the suppressed and active regions is strong and is relatively insensitive to the degree of the coupling. Additionally, scaling arguments are developed for the relative values of the terms in the mechanical energy budget.

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42

Skyllingstad, Eric D., e Simon P. de Szoeke. "Cloud-Resolving Large-Eddy Simulation of Tropical Convective Development and Surface Fluxes". Monthly Weather Review 143, n. 7 (1 luglio 2015): 2441–58. http://dx.doi.org/10.1175/mwr-d-14-00247.1.

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Abstract Cloud-resolving large-eddy simulations (LES) on a 500 km × 500 km periodic domain coupled to a thermodynamic ocean mixed layer are used to study the effect of large-scale moisture convergence M on the convective population and heat and moisture budgets of the tropical atmosphere, for several simulations with M representative of the suppressed, transitional, and active phases of the Madden–Julian oscillation (MJO). For a limited-area model without an imposed vertical velocity, M controls the overall vertical temperature structure. Moisture convergence equivalent to ~200 W m−2 (9 mm day−1) maintains the observed temperature profile above 5 km. Increased convective heating for simulations with higher M is partially offset by greater infrared cooling, suggesting a potential negative feedback that helps maintain the weak temperature gradient conditions observed in the tropics. Surface evaporation decreases as large-scale moisture convergence increases, and is only a minor component of the overall water budget for convective conditions representing the active phase of the MJO. Cold pools generated by evaporation of precipitation under convective conditions are gusty, with roughly double the wind stress of their surroundings. Consistent with observations, enhanced surface evaporation due to cold pool gusts is up to 40% of the mean, but has a small effect on the total moisture budget compared to the imposed large-scale moisture convergence.

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43

Vogel, Sven C., Helmut Reiche e Donald W. Brown. "High pressure deformation study of zirconium". Powder Diffraction 22, n. 2 (giugno 2007): 113–17. http://dx.doi.org/10.1154/1.2737459.

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In situ deformation studies of polycrystalline materials using diffraction are an established method to understand elastic and plastic deformation of materials. Studies of active deformation mechanisms, the interplay of deformation with texture, and ultimately the development of predictive capabilities for deformation modeling are an active field of research. Parameters studied by diffraction are typically lattice strains and texture evolution, which coupled with the macroscopic flow curve allow for improved understanding of the micro-mechanics of deformation. We performed a study of the uniaxial deformation of Zircaloy-2 at 2 GPa at the 13-BM-D beamline at the Advanced Photon Source. The deformation-DIA apparatus generates a confining hydrostatic pressure using a cubic anvil setup. Two differential rams allow an increase (compressive load) or decrease (tensile load) of the uniaxial straining in the vertical direction, allowing studies of plastic deformation at high pressures. In this paper, we describe how macroscopic strains, hydrostatic pressure, and uniaxial strains are derived and present some brief results.

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44

Mignot, J., A. Ganopolski e A. Levermann. "Atlantic Subsurface Temperatures: Response to a Shutdown of the Overturning Circulation and Consequences for Its Recovery". Journal of Climate 20, n. 19 (1 ottobre 2007): 4884–98. http://dx.doi.org/10.1175/jcli4280.1.

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Abstract Using the coupled climate model of intermediate complexity, CLIMBER-3α, changes in the vertical thermal structure associated with a shutdown of the Atlantic meridional overturning circulation (AMOC) are investigated. When North Atlantic Deep Water formation is inhibited by anomalous freshwater forcing, intermediate depth ventilation can remain active and cool the subsurface water masses (i.e., the “cold case”). However, if intermediate ventilation is completely suppressed, relatively warm water coming from the south penetrates to a high northern latitude beneath the halocline and induces a strong vertical temperature inversion between the surface and intermediate depth (i.e., the “warm case”). Both types of temperature anomalies emerge within the first decade after the beginning of the freshwater perturbation. The sign of subsurface temperature anomaly has a strong implication for the recovery of the AMOC once the anomalous freshwater forcing is removed. While the AMOC recovers from the cold case on centennial time scales, the recovery is much more rapid (decadal time scales) when ventilation is completely suppressed and intermediate depths are anomalously warm. This is explained by a more rapid destabilization of the water column after cessation of the anomalous flux due to a strong vertical temperature inversion. A suite of sensitivity experiments with varying strength and duration of the freshwater perturbation and a larger value of background vertical diffusivity demonstrate robustness of the phenomenon. Implications of the simulated subsurface temperature response to the shutdown of the AMOC for future climate and abrupt climate changes of the past are discussed.

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45

ARMENIO, VINCENZO, e SUTANU SARKAR. "An investigation of stably stratified turbulent channel flow using large-eddy simulation". Journal of Fluid Mechanics 459 (25 maggio 2002): 1–42. http://dx.doi.org/10.1017/s0022112002007851.

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Boundary-forced stratified turbulence is studied in the prototypical case of turbulent channel flow subject to stable stratification. The large-eddy simulation approach is used with a mixed subgrid model that involves a dynamic eddy viscosity component and a scale-similarity component. After an initial transient, the flow reaches a new balanced state corresponding to active wall-bounded turbulence with reduced vertical transport which, for the cases in our study with moderate-to-large levels of stratification, coexists with internal wave activity in the core of the channel. A systematic reduction of turbulence levels, density fluctuations and associated vertical transport with increasing stratification is observed. Countergradient buoyancy flux is observed in the outer region for sufficiently high stratification.Mixing of the density field in stratified channel flow results from turbulent events generated near the boundaries that couple with the outer, more stable flow. The vertical density structure is thus of interest for analogous boundary-forced mixing situations in geophysical flows. It is found that, with increasing stratification, the mean density profile becomes sharper in the central region between the two turbulent layers at the upper and lower walls, similar to observations in field measurements as well as laboratory experiments with analogous density-mixing situations.Channel flow is strongly inhomogeneous with alternative choices for the Richardson number. In spite of these complications, the gradient Richardson number, Rig, appears to be the important local determinant of buoyancy effects. All simulated cases show that correlation coefficients associated with vertical transport collapse from their nominal unstratified values over a narrow range, 0.15 < Rig < 0.25. The vertical turbulent Froude number, Frw, has an O(1) value across most of the channel. It is remarkable that stratified channel flow, with such a large variation of overall density difference (factor of 26) between cases, shows a relatively universal behaviour of correlation coefficients and vertical Froude number when plotted as a function of Rig. The visualizations show wavy motion in the core region where the gradient Richardson number, Rig, is large and low-speed streaks in the near-wall region, typical of unstratified channel flow, where Rig is small. It appears from the visualizations that, with increasing stratification, the region with wavy motion progressively encroaches into the zone with active turbulence; the location of Rig ≃ 0.2 roughly corresponds to the boundary between the two zones.

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46

KANG, HUSEN KARTASASMITA, CHEE CHEONG WONG, FILIPPO ROMANATO, A. PISTORE e G. BRUSATIN. "SENSITIVITY OF PLASMONIC CRYSTAL WITH ACTIVE SOL–GEL THIN FILM". International Journal of Nanoscience 08, n. 01n02 (febbraio 2009): 131–35. http://dx.doi.org/10.1142/s0219581x09005797.

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Plasmonic crystal or gratings with periodicity and amplitudes suitable for plasmon coupling can be fabricated using interference lithography technique. The grating structure is holographically formed in a photoresist film. This technique offers an easy way to control the vertical and horizontal ratio of the corrugated profile. Since surface polaritons are extremely sensitive to the changes at the metallic and dielectric interface, one can expect that by controlling this refractive index, an effective control of the SPP can be realized. Different diffracted orders can be explored by controlling the dielectric medium, in this case hybrid materials. A comprehensive simulation that models the effect of dielectric medium to the changes of SPP coupling condition has been undertaken for the reflectivity and azimuthal angle dependence. An active porous thin film, which is hybrid organic–inorganic materials synthesized by sol–gel techniques, starting from bridged polysilsesquioxanes with phenol red, is coupled on plasmonic crystals in order to exploit enhanced effective refractive index sensitivity for sensing purposes; in this case, we use hydrochloric acid as analyte. The porosity of film increases reacting surface area and chemical reactivity of the plasmonic crystal. This film will change color from yellow to orange red when exposed to the acid. The change of optical characteristic after matrix wetting in HCl 0.01 molar solution has also been characterized. The activity of the film is determined by the dielectric properties depending on an applied external electric and magnetic field. They constitute molecular-engineered materials that exhibit a fine control in porosity in order to control the permittivity of the dielectric medium. The optical, thermal, and structural characterizations of these films are investigated by ellipsometry, DTA, and FTIR measurements. We present this configuration as a sensitive architecture for plasmonic-based sensor application.

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47

Надточий, А. М., Ю. М. Шерняков, М. М. Кулагина, А. С. Паюсов, Н. Ю. Гордеев, М. В. Максимов, А. Е. Жуков et al. "Инжекционные лазеры InGaAlP/GaAs оранжевого оптического диапазона (~600 нм)". Физика и техника полупроводников 53, n. 12 (2019): 1708. http://dx.doi.org/10.21883/ftp.2019.12.48631.9217.

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Lasing in orange spectral range(599−605 nm)in(AlxGa1−x)0.5In0.5P−GaAs laser diodes grown by MOVPE on GaAs substrates(211) and (322) was demonstrated. The active region consisted of 4 layers of InxGa1−xP vertically coupled quantum dots. Carrier leakage from the active area was suppressed by using barriers formed with 4 quantum-sized layers of InGaAlP with high Ga content. The maximum optical power in the pulsed regime was limited by catastrophic optical mirror degradation and reached 800 mW. Lower threshold current density, higher differential efficiency, and lower internal losses were demonstrated by lasers processed from epitaxial structures grown on(322)A substrates in comparison to those grown on(211)A. This fact is due to the higher energy barrier for electrons in the first case.

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48

Zhao, Haojin, Carsten Montzka, Roland Baatz, Harry Vereecken e Harrie-Jan Hendricks Franssen. "The Importance of Subsurface Processes in Land Surface Modeling over a Temperate Region: An Analysis with SMAP, Cosmic Ray Neutron Sensing and Triple Collocation Analysis". Remote Sensing 13, n. 16 (4 agosto 2021): 3068. http://dx.doi.org/10.3390/rs13163068.

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Land surface models (LSMs) simulate water and energy cycles at the atmosphere–soil interface, however, the physical processes in the subsurface are typically oversimplified and lateral water movement is neglected. Here, a cross-evaluation of land surface model results (with and without lateral flow processes), the National Aeronautics and Space Administration (NASA) Soil Moisture Active/Passive (SMAP) mission soil moisture product, and cosmic-ray neutron sensor (CRNS) measurements is carried out over a temperate climate region with cropland and forests over western Germany. Besides a traditional land surface model (the Community Land Model (CLM) version 3.5), a coupled land surface-subsurface model (CLM-ParFlow) is applied. Compared to CLM stand-alone simulations, the coupled CLM-ParFlow model considered both vertical and lateral water movement. In addition to standard validation metrics, a triple collocation (TC) analysis has been performed to help understanding the random error variances of different soil moisture datasets. In this study, it is found that the three soil moisture datasets are consistent. The coupled and uncoupled model simulations were evaluated at CRNS sites and the coupled model simulations showed less bias than the CLM-standalone model (−0.02 cm3 cm−3 vs. 0.07 cm3 cm−3), similar random errors, but a slightly smaller correlation with the measurements (0.67 vs. 0.71). The TC-analysis showed that CLM-ParFlow reproduced better soil moisture dynamics than CLM stand alone and with a higher signal-to-noise ratio. This suggests that the representation of subsurface physics is of major importance in land surface modeling and that coupled land surface-subsurface modeling is of high interest.

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49

Li, Nansong, Minghui Zhang e Bo Gao. "Horizontal Correlation of Long-Range Bottom Reverberation in Shallow Sloping Seabed". Journal of Marine Science and Engineering 9, n. 4 (13 aprile 2021): 414. http://dx.doi.org/10.3390/jmse9040414.

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The performance of active sonar detection systems is seriously affected by the reverberation at the bottom of the waveguide in shallow water. In order to improve the performance of active sonar detection, it is necessary to understand the horizontal correlation of shallow-water bottom reverberation in active towed-array processing technology. However, the current research on the spatial correlation of reverberation is mainly based on vertical correlation, little work has been done on the horizontal correlation characteristics of long-distance seabed reverberation, and there is no support from sea test data. In this paper, the coupled mode reverberation model is applied to the horizontal correlation, and is studied according to the receiving position, time, and frequency. The simulation results show that, for the long-range bottom reverberation, the lateral correlation is greater than the longitudinal correlation in the horizontal space. By introducing the adiabatic mode solution, the mathematical model of horizontal correlation in the range-dependent waveguide with depth is derived. The numerical results show that the influence of the seabed dip angle on the horizontal correlation should be considered and that the horizontal correlation is affected obviously by the propagation effects of the sloped sea floor. Finally, the experimental data processing and analysis are given and verify the correctness of the algorithm.

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50

Williams, Alastair G., Wlodek Zahorowski, Scott Chambers, Alan Griffiths, Jörg M. Hacker, Adrian Element e Sylvester Werczynski. "The Vertical Distribution of Radon in Clear and Cloudy Daytime Terrestrial Boundary Layers". Journal of the Atmospheric Sciences 68, n. 1 (1 gennaio 2011): 155–74. http://dx.doi.org/10.1175/2010jas3576.1.

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Abstract Radon (222Rn) is a powerful natural tracer of mixing and exchange processes in the atmospheric boundary layer. The authors present and discuss the main features of a unique dataset of 50 high-resolution vertical radon profiles up to 3500 m above ground level, obtained in clear and cloudy daytime terrestrial boundary layers over an inland rural site in Australia using an instrumented motorized research glider. It is demonstrated that boundary layer radon profiles frequently exhibit a complex layered structure as a result of mixing and exchange processes of varying strengths and extents working in clear and cloudy conditions within the context of the diurnal cycle and the synoptic meteorology. Normalized aircraft radon measurements are presented, revealing the characteristic structure and variability of three major classes of daytime boundary layer: 1) dry convective boundary layers, 2) mixed layers topped with residual layers, and 3) convective boundary layers topped with coupled nonprecipitating clouds. Robust and unambiguous signatures of important atmospheric processes in the boundary layer are identifiable in the radon profiles, including “top-down” mixing associated with entrainment in clear-sky cases and strongly enhanced venting and subcloud-layer mixing when substantial active cumulus are present. In poorly mixed conditions, radon gradients in the daytime atmospheric surface layer significantly exceed those predicted by Monin–Obukhov similarity theory. In two case studies, it is demonstrated for the first time that a sequence of vertical radon profiles measured over the course of a single day can consistently reproduce major structural features of the evolving boundary layer.

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