scholarly journals Study of Forward and Backward Modes in Double-Sided Dielectric-Filled Corrugated Waveguides

Sensors ◽  
2021 ◽  
Vol 21 (18) ◽  
pp. 6293
Author(s):  
Pilar Castillo-Tapia ◽  
Francisco Mesa ◽  
Alexander Yakovlev ◽  
Guido Valerio ◽  
Oscar Quevedo-Teruel
Keyword(s):  
Cutoff Frequency ◽  
Resonant Mode ◽  
Symmetric Case ◽  
Transmission Matrix ◽  
Propagation Characteristics ◽  
Hollow Waveguide ◽  
Rejection Level ◽  
Corrugated Waveguides ◽  
Backward Propagation ◽  
The Impact

This work studies the propagation characteristics of a rectangular waveguide with aligned/ misaligned double-sided dielectric-filled metallic corrugations. Two modes are found to propagate in the proposed double-sided configuration below the hollow-waveguide cutoff frequency: a quasi-resonant mode and a backward mode. This is in contrast to the single-sided configuration, which only allows for backward propagation. Moreover, the double-sided configuration can be of interest for waveguide miniaturization on account of the broader band of its backward mode. The width of the stopband between the quasi-resonant and backward modes can be controlled by the misalignment of the top and bottom corrugations, being null for the glide-symmetric case. The previous study is complemented with numerical results showing the impact of the height of the corrugations, as well as the filling dielectric permittivity, on the bandwidth and location of the appearing negative-effective-permeability band. The multi-modal transmission-matrix method has also been employed to estimate the rejection level and material losses in the structure and to determine which port modes are associated with the quasi-resonant and backward modes. Finally, it is shown that glide symmetry can advantageously be used to reduce the dispersion and broadens the operating band of the modes.

scholarly journals A Comparison of the Downstream Predictability Associated with ET and Baroclinic Cyclones

2017 ◽  
Vol 145 (11) ◽  
pp. 4651-4672 ◽  
Author(s):  
Ryan D. Torn
Keyword(s):  
Standard Deviation ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
North Pacific ◽  
Western North Pacific ◽  
Ensemble Forecast ◽  
Latent Heat Release ◽  
Propagation Characteristics ◽  
Forecast System ◽  
The Impact

The impact of the extratropical transition (ET) of tropical cyclones and baroclinic cyclogenesis in the western North Pacific (WNP), Atlantic, and southern Indian Ocean (SIO) basins on the predictability of the downstream midlatitude flow is assessed using 30 years of cases from the Global Ensemble Forecast System (GEFS) Reforecast, version 2. In all three basins, ET is associated with statistically larger 500-hPa geopotential height forecast standard deviation (SD) compared to the forecast climatology. The higher SD values originate from where the TC enters the midlatitudes and spread downstream at the group velocity of the associated wave packet. Of the three basins, WNP ET is associated with the largest amplitude and longest-lasting SD anomalies. Forecasts initialized 2–4 days prior to the onset of ET have larger SD anomalies compared to forecasts initialized during or after the onset of ET. By contrast, the region of positive SD anomaly associated with winter baroclinic cyclones is confined to the upstream trough, with fall cyclones exhibiting some downstream propagation characteristics similar to ET. The ET cases with the larger downstream SD anomaly are characterized by a more amplified ridge downstream of the TC as it enters the midlatitudes. By contrast, ET cases with an upstream trough, large TC position variability at the onset of ET, latent heat release, or upper-tropospheric PV advection by the irrotational wind are not characterized by significantly larger downstream SD compared to cases without an upstream trough or smaller values of these quantities.

The Influence of Metal Layer on the Differential Transformer Displacement Sensor

2011 ◽  
Vol 121-126 ◽  
pp. 3594-3601
Author(s):  
Chao Wu Jin ◽  
Long Xiang Xu ◽  
Qiu Ping Fan ◽  
Yi Li Zhu
Keyword(s):  
Metal Layer ◽  
Cutoff Frequency ◽  
External Environment ◽  
Displacement Sensor ◽  
Impact Factors ◽  
Active Magnetic Bearings ◽  
Test Bed ◽  
Amb System ◽  
The Impact ◽  
Metal Layers

For some special active magnetic bearings (AMBs) application occasions that demand the rotor isolated from external environment, especially when a metal layer is added, other sensors besides differential transformer displacement sensor (DTDS) can not used to detect the rotor displacements. Before being used, the impact factors and relevant extents on the DTDS performances are analyzed on the basis of magnetic and electrical properties the added metal layer between the DTDS core and the measured object. The DTDS performance with and without metal layers are separately simulated on the platform of MATLAB and ANSOFT. And then the DTDS with metal layers are applied to a five-DOF AMB test bed. The research results show that the sensor sensitivity has decreased 8.18% and cutoff frequency decreased 5%, while the linearity increased 38.7%. Despite of those changes, the rotor can also be stably suspended and rotated at 30 000r/min in the five-DOF AMB system.

Simulation of borehole sonic waveforms in dipping, anisotropic, and invaded formations

Geophysics ◽  
2011 ◽  
Vol 76 (4) ◽  
pp. E127-E139 ◽  
Author(s):  
Robert K. Mallan ◽  
Carlos Torres-Verdín ◽  
Jun Ma
Keyword(s):  
Wave Propagation ◽  
Shear Modulus ◽  
Symmetry Axis ◽  
Transverse Isotropy ◽  
Cutoff Frequency ◽  
Dispersion Curves ◽  
Flexural Wave ◽  
Stoneley Wave ◽  
Stoneley Waves ◽  
The Impact

A numerical simulation study has been made of borehole sonic measurements that examined shoulder-bed, anisotropy, and mud-filtrate invasion effects on frequency-dispersion curves of flexural and Stoneley waves. Numerical simulations were considered for a range of models for fast and slow formations. Computations are performed with a Cartesian 3D finite-difference time-domain code. Simulations show that presence of transverse isotropy (TI) alters the dispersion of flexural and Stoneley waves. In slow formations, the flexural wave becomes less dispersive when the shear modulus (c44) governing wave propagation parallel to the TI symmetry axis is lower than the shear modulus (c66) governing wave propagation normal to the TI symmetry axis; conversely, the flexural wave becomes more dispersive when c44 > c66. Dispersion decreases by as much as 30% at higher frequencies for the considered case where c44 < c66. Dispersion of Stoneley waves, on the other hand, increases in TI formations when c44 > c66 and decreases when c44 < c66. Dispersion increases by more than a factor of 2.5 at higher frequencies for the considered case where c44 < c66. Simulations also indicate that the impact of invasion on flexural and Stoneley dispersions can be altered by the presence of TI. For the case of a slow formation and TI, where c44 decreases from the isotropic value, separation between dispersion curves for cases with and without the presence of a fast invasion zone increases by as much as 33% for the flexural wave and by as much as a factor of 1.4 for the Stoneley wave. Lastly, presence of a shoulder bed intersecting the sonic tool at high dip angles can alter flexural dispersion significantly at low frequencies. For the considered case of a shoulder bed dipping at 80°, ambiguity in the flexural cutoff frequency might lead to shear-wave velocity errors of 8%–10%.

scholarly journals Meander-DGS Effect on Electromagnetic Bandgap Structure for Power/Ground Noise Suppression in High-Speed Integrated Circuit Packages and PCBs

Electronics ◽  
2022 ◽  
Vol 11 (2) ◽  
pp. 211
Author(s):  
Myunghoi Kim
Keyword(s):  
Slow Wave ◽  
Integrated Circuit ◽  
Analytical Method ◽  
High Speed ◽  
Noise Suppression ◽  
Cutoff Frequency ◽  
Closed Form Expression ◽  
Electromagnetic Bandgap ◽  
Ground Noise ◽  
The Impact

In this paper, we present the impact of a meander-shaped defected ground structure (MDGS) on the slow-wave characteristics of a lowest-order passband and a low cutoff frequency of the first stopband of an electromagnetic bandgap (EBG) structure for power/ground noise suppression in high-speed integrated circuit packages and printed circuit boards (PCBs). A semi-analytical method is presented to rigorously analyze the MDGS effect. In the analytical method, a closed-form expression for a low cutoff frequency of the MDGS-EBG structure is extracted with an effective characteristic impedance and a slow-wave factor. The proposed analytical method enables the fast analysis of the MDGS-EBG structure so that it can be easily optimized. The analysis of the MDGS effect revealed that the low cutoff frequency increases up to approximately 19% while comparing weakly and strongly coupled MDGSs. It showed that the miniaturization of the MDGS-EBG structure can be achieved. It was experimentally verified that the low cutoff frequency is reduced from 2.54 GHz to 2.00 GHz by decreasing the MDGS coupling coefficient, which is associated with the miniaturization of the MDGS-EBG structure in high-speed packages and PCBs.

Defect-Induced Mechanical Mode Splitting in Carbon Nanotube Resonators

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Ajit K. Vallabhaneni ◽  
Jeffrey F. Rhoads ◽  
Jayathi Y. Murthy ◽  
Xiulin Ruan
Keyword(s):  
Carbon Nanotube ◽  
Md Simulations ◽  
Resonant Mode ◽  
Mass Sensing ◽  
Response Characteristics ◽  
Future Design ◽  
Mode Splitting ◽  
Design Paradigm ◽  
The Impact ◽  
Current Device

This work examines the impact of defects on the resonant response of single-wall carbon nanotube (CNT) resonators using classical molecular dynamics (MD) simulations. The work demonstrates that the presence of defects in CNTs leads to appreciable resonant mode splitting. A dimensionless parameter has been introduced to quantify this phenomenon. It is observed that increasing the degree of asymmetry in the system generally increases the magnitude of splitting. Given the centrality of single-peak Lorentzian frequency responses in the current device design paradigm, which is utilized in applications such as resonant mass sensing, the non-Lorentzian response characteristics of imperfect devices could present both opportunities and challenges in the future design and development of resonant nanosystems.

scholarly journals Use of a Rain Gauge Network to Infer the Influence of Environmental Factors on the Propagation of Quasi-Linear Convective Systems in West Africa

2007 ◽  
Vol 22 (5) ◽  
pp. 1016-1030 ◽  
Author(s):  
Jon M. Schrage ◽  
Andreas H. Fink
Keyword(s):  
Environmental Factors ◽  
Propagation Rate ◽  
Rain Gauge ◽  
West African ◽  
Squall Line ◽  
Propagation Characteristics ◽  
Convective Systems ◽  
Squall Lines ◽  
Radiosonde Station ◽  
The Impact

Abstract The West African squall line is a key quasi-linear storm system that brings much of the precipitation observed in the data-poor Sudanian climate zone. Squall lines propagate at a wide range of speeds and headings, but the lack of operational radar stations in the region makes quantifying the propagation of the squall lines difficult. A new method of estimating the propagation rate and heading for squall lines is proposed. Based on measurements of the time of onset of precipitation (OOP) at a network of rain gauge stations, an estimate of the propagation characteristics of the squall line can be inferred. By combining estimates of propagation rate with upper-air observations gathered at a nearby radiosonde station, the impact of various environmental factors on the propagation characteristics of West African squall lines is inferred. Results suggest that the propagation speed for West African squall lines is related to the conditions at midtropospheric levels, where dry air and an enhanced easterly flow favor faster propagation. Northerly anomalies at these levels are also associated with faster propagation. When applied to West African squall lines, the correlations between these environmental factors and the speed of propagation are significantly higher than those of methods developed for mesoscale convective systems in other parts of the world.

Application of the Modal Approach for Prediction of Forced Response Amplitudes for Fan Blades

2018 ◽  
Author(s):  
Franziska Eichner ◽  
Joachim Belz
Keyword(s):  
Energy Method ◽  
Natural Frequencies ◽  
Resonant Mode ◽  
Forced Response ◽  
Vibrational Amplitude ◽  
Campbell Diagram ◽  
Modal Approach ◽  
Blade Row ◽  
The Impact ◽  
Blade Row Interaction

Forced response is the main reason for high cycle fatigue in turbomachinery. Not all resonance points in the operating range can be avoided especially for low order excitation. For highly flexible CFRP fans an accurate calculation of vibration amplitudes is required. Forced response analyses were performed for blade row interaction and boundary layer ingestion. The resonance points considered were identified in the Campbell diagram. Forced response amplitudes were calculated using a modal approach and results are compared to the widely used energy method. For the unsteady simulations a time-linearised URANS method was applied. If only the resonant mode was considered the forced response amplitude from the modal approach was confirmed with the energy method. Thereby forced response due to BLI showed higher vibration amplitudes than for blade row interaction. The impact of modes which are not in resonant to the total deformation were investigated by using the modal approach, which so far, only considers one excitation order. A doubling of vibrational amplitude was shown in the case of blade row interaction for higher rotational speeds. The first and third mode-shape as well as modes with similar natural frequencies were identified as critical cases. The behaviour in the vicinity of resonance shows high vibration amplitudes over a larger frequency range. This is also valid for high modes with many nodal diameters, which have a greater risk of critical strain.

scholarly journals Preliminary results from the MEMO multicomponent measurements of waves on-board INTERBALL 2

1998 ◽  
Vol 16 (9) ◽  
pp. 1117-1136 ◽  
Author(s):  
F. Lefeuvre ◽  
M. Parrot ◽  
J. L. Rauch ◽  
B. Poirier ◽  
A. Masson ◽  
...  
Keyword(s):  
Cutoff Frequency ◽  
Accurate Estimation ◽  
Magnetic Field Direction ◽  
Propagation Characteristics ◽  
High Resolution Data ◽  
Source Regions ◽  
Electromagnetic Emissions ◽  
Instruments And Techniques ◽  
Auroral Phenomena ◽  
Wave Normal

Abstract. The MEMO (MEsure Multicomposante des Ondes) experiment is a part of the INTERBALL 2 wave consortium. It is connected to a total of six electric and nine magnetic independent sensors. It provides waveforms associated with the measurement of two to five components in three frequency bands: ELF (5–1000 Hz), VLF (1–20 kHz), LF (20–250 kHz). Preliminary analyses of low and high resolution data are presented. The emphasis is put on the estimation of the propagation characteristics of the observed waves.VLF hiss emissions are shown to be mainly whistler mode emissions, but other modes are present. An accurate estimation of the local plasma frequency is proposed when the low L = 0 cutoff frequency is identified. AKR emissions observed just above source regions are studied. R-X and L-O modes are found: the first at the lowest frequencies and the second at the highest. Both propagate with wave normal directions weakly oblique or quasi-parallel to the Earth's magnetic field direction. Propagation characteristics are also determined for a (non-drifting) fine structure of AKR. There is no fundamental difference with structurless events. Nightside and dayside bursts of ELF electromagnetic emissions are presented. It is not clear whether the two emissions belong to the "lion roar" emissions or not.Key words. Magnetospheric physics (auroral phenomena; plasma waves and instabilities; instruments and techniques)

Longitudinal- and transverse-operators formalism for chiral media: Application to guided structures filled with chiral materials

2004 ◽  
Vol 82 (5) ◽  
pp. 367-378 ◽  
Author(s):  
R Oussaid ◽  
B Haraoubia
Keyword(s):  
Wave Propagation ◽  
Electromagnetic Wave ◽  
Parallel Plate ◽  
Electromagnetic Wave Propagation ◽  
Cutoff Frequency ◽  
Mathematical Approach ◽  
Propagation Characteristics ◽  
Chiral Media ◽  
Medium Components ◽  
Chiral Materials

In this paper an approach based on the calculation of longitudinal and transverse operators is presented. The paper is devoted to the interesting topic of electromagnetic-wave propagation in complex (chiral) media. The studied process allows the analysis of guidedstructures with chiral-medium components. In this case the equations are continuously coupled. Using the longitudinal equations, we analyze wave propagation in a parallel-plate chirowaveguide consisting of two parallel perfectly conducting planes filled with a lossless, homogeneous, isotropic chiral material. The main feature of the guides is that the propagation modes are always hybrid. In addition, bifurcated modes exist with the same cutoff-frequency values and unequal propagation characteristics. We address here the issue of wave propagation in a rectangular chirowaveguide, by means of longitudinal and transverse operators. This topic was first addressed by Engheta and Pelet. (IEEE Trans. Antenna Propag. 38, 90 (1990)). We rederive their results, using a method based on a new mathematical approach that seems to be original.PACS Nos.: 41.20.Jb

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