A numerical study on multimode sound propagation in lined ducts and radiation to the far field

2008 ◽  
Vol 123 (5) ◽  
pp. 3128-3128
Author(s):  
Rie Sugimoto ◽  
R Jeremy Astley ◽  
Claire R. McAleer ◽  
Iansteel Achunche
Keyword(s):  
Sound Propagation ◽  
Numerical Study ◽  
Far Field ◽  
Lined Ducts

Time-domain calculation of sound propagation in lined ducts with sheared flows

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 768-773 ◽  
Author(s):  
Yusuf Ozyoruk ◽  
Lyle N. Long
Keyword(s):  
Time Domain ◽  
Sound Propagation ◽  
Sheared Flows ◽  
Lined Ducts

scholarly journals NEGATIVE REFRACTION AND SUBWAVELENGTH FOCUSING USING PHOTONIC CRYSTALS

2004 ◽  
Vol 18 (25) ◽  
pp. 1275-1291 ◽  
Author(s):  
EKMEL OZBAY ◽  
KAAN GUVEN ◽  
ERTUGRUL CUBUKCU ◽  
KORAY AYDIN ◽  
B. KAMIL ALICI
Keyword(s):  
Optical Properties ◽  
Photonic Crystals ◽  
Negative Refraction ◽  
Numerical Study ◽  
Effective Index ◽  
Index Of Refraction ◽  
Far Field ◽  
Two Dimensional ◽  
Flat Lens ◽  
Effective Index Of Refraction

In this article, we present an experimental and numerical study of novel optical properties of two-dimensional dielectric photonic crystals (PCs) which exhibit negative refraction. We investigate two mechanisms which utilize the band structure of the PC to generate a negative effective index of refraction (n eff <0) and demonstrate the negative refraction experimentally. To the isotropic extend of n eff , different PC slab structures are employed to focus the radiation of a point source. It is shown experimentally that the PC can generate an image of the source with subwavelength resolution in the vicinity of the PC interface. Using a different PC, one can also obtain a far field focusing. In the latter case, we explicitly show the flat lens behavior of the structure. These examples indicate that PC-based lenses can surpass limitations of conventional lenses and lead to novel optics applications.

scholarly journals Sound propagation in the near and far-field of a broadband echolocating dolphin and a narrowband echolocating porpoise

2019 ◽  
Author(s):  
Chong Wei ◽  
Whitlow W. L. Au ◽  
Darlene R. Ketten ◽  
Hari Vishnu ◽  
Abel Zhong Hao Ho
Keyword(s):  
Sound Propagation ◽  
Far Field

Numerical study of terahertz circular polarized substrate lens dipole antennas for polarization sensitive detectors

2015 ◽  
Vol 8 (3) ◽  
pp. 623-631
Author(s):  
Amna Mir ◽  
Junsheng Yu ◽  
Xiaodong Chen ◽  
Ishtiaq Ahmad
Keyword(s):  
Numerical Study ◽  
Wide Band ◽  
Cd Spectroscopy ◽  
Internal Reflection ◽  
Point Of View ◽  
Far Field ◽  
Dipole Antennas ◽  
Planar Antennas ◽  
Field Patterns ◽  
Feeding Structure

Wide band circular polarized (CP) antennas behind extended hemispherical lenses suitable for polarization sensitive THz detector and wireless communication have been designed and characterized using numerical simulation. Two novel, compact and CP dipole antennas are designed and studied for this purpose. CP property of planar antennas is achieved by geometrical modifications of antennas without any complicated feeding structure. Due to compact dimensions, wideband performance and CP behavior, these designs have applications in circular dichroism (CD) spectroscopy and terahertz detectors. This numerical study deals with polarization diversity with substrate lens, effect of off axis displacement on CP behavior of lens antenna which determines number of pixels for any application, far field patterns variation due to lens's internal reflection, directivity variation attributed to internal reflection and losses. Radiation efficiency variation of antenna by antenna dimensions is also studied carefully to design appropriate lens from application's point of view. Off axis performance of antenna on hemisphere lens is also studied and redesigning of antenna by some geometric modification has been carried out to improve far field patterns.

scholarly journals Numerical Study of the Seismic Efficiency of Buckling-Restrained Braces for Near and Far-Fault Inputs

2015 ◽  
Vol 9 (1) ◽  
pp. 281-294
Author(s):  
G.L. Palazzo ◽  
P. Martín ◽  
F. Calderón ◽  
V. Roldán ◽  
F. López-Almansa
Keyword(s):  
Dynamic Response ◽  
Numerical Study ◽  
Experimental Studies ◽  
Time Interval ◽  
Short Time Interval ◽  
Far Field ◽  
Near Fault ◽  
Buckling Restrained Braces ◽  
Seismic Records ◽  
Far Fault

Buckling-restrained braces are commonly installed in building structures as concentric diagonal or chevron braces to protect the main construction from seismic actions. These elements have shown repeatedly their usefulness for reducing the seismic response, both from theoretical and experimental studies; and a number of practical applications have been reported. However, seismic records with near-fault effects possess special characteristics that might impair the performance of these devices, similarly as what occurs in base isolation; about energy issues, in such records (containing strong velocity pulses) the energy is delivered in a short time interval, thus being difficult to be absorbed. This work presents a numerical study regarding the performance of buckling-restrained braces under three types of seismic records: cortical far-field, subductive far-field and near-field (i.e. containing velocity pulses). The study is carried out on a symmetric 4-story steel moment-resisting unbraced frame that was tested at the E-defense laboratory, Japan; the dynamic response of such unbraced bare frame is numerically simulated, obtaining a satisfactory agreement. The same numerical model is used to describe the 2-D dynamic behavior of the steel frame equipped with buckling-restrained braces. The inputs are three series of ten ground motion records; each of these series belongs to one of the three aforementioned types. The average responses for each of the three types of inputs are compared; the obtained results show that the buckling-restrained braces are able to reduce the dynamic response of the frame and that no significant differences can be observed among the efficiency for far-fault and near- fault records.

Far Field Optical Properties of a Monolayer of SiO2 Spheres and Small Au Nanoparticles

MRS Advances ◽  
2018 ◽  
Vol 3 (64) ◽  
pp. 3917-3923 ◽  
Author(s):  
A. Santos Gómez ◽  
A. L. González
Keyword(s):  
Numerical Study ◽  
Normal Incidence ◽  
Dipole Approximation ◽  
Silica Spheres ◽  
Far Field ◽  
Approximation Model ◽  
Au Nps ◽  
Transmission And Absorption ◽  
Sio2 Spheres ◽  
Hexagonal Closed Packed

ABSTRACTHere, we present a numerical study of the far field optical response of a monolayer composed by an hexagonal closed packed array of SiO2 spheres with a single Au NP at each interstitial position. The Optical Efficiencies, Reflection, Transmission and Absorption at normal incidence, were calculated using Discrete Dipole Approximation model extended to periodic targets. In order to consider different amounts of loads of Au NPs per unit of area in the monolayer, we have fixed the diameter of Au NPs (9 nm) and varied the diameter of the SiO2 spheres. The numerical calculations indicate that Au-SiO2 composite monolayers can absorb and scatter the incident electromagnetic wave, as the load of Au NPs increases the monolayer becomes less transparent to light and the spectra are red-shifted. The profile of the absorption spectrum of the Au-SiO2 composite monolayer is very similar to that of a Au NPs monolayer (composite monolayer without the Silica spheres) but less intense, presumably because the Silica spheres screen the coupling of the Localized Surface Plasmons of Au NPs.

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