scholarly journals Numerical simulations of near-field head-related transfer functions: Magnitude verification and validation with laser spark sources

2020 ◽  
Vol 148 (1) ◽  
pp. 153-166
Author(s):  
Sebastian T. Prepeliţă ◽  
Javier Gómez Bolaños ◽  
Ville Pulkki ◽  
Lauri Savioja ◽  
Ravish Mehra
Keyword(s):  
Numerical Simulations ◽  
Transfer Functions ◽  
Near Field ◽  
Verification And Validation ◽  
Laser Spark

scholarly journals Optical near-field mapping of plasmonic nanostructures prepared by nanosphere lithography

2018 ◽  
Vol 9 ◽  
pp. 1536-1543 ◽  
Author(s):  
Gitanjali Kolhatkar ◽  
Alexandre Merlen ◽  
Jiawei Zhang ◽  
Chahinez Dab ◽  
Gregory Q Wallace ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Hot Spots ◽  
Near Field ◽  
Nanosphere Lithography ◽  
Plasmonic Nanostructures ◽  
Far Field ◽  
Optical Images ◽  
Spatial Frequencies ◽  
Comparison Of The Results ◽  
Non Destructive

We introduce a simple, fast, efficient and non-destructive method to study the optical near-field properties of plasmonic nanotriangles prepared by nanosphere lithography. Using a rectangular Fourier filter on the blurred signal together with filtering of the lower spatial frequencies to remove the far-field contribution, the pure near-field contributions of the optical images were extracted. We performed measurements using two excitation wavelengths (532.1 nm and 632.8 nm) and two different polarizations. After the processing of the optical images, the distribution of hot spots can be correlated with the topography of the structures, as indicated by the presence of brighter spots at the apexes of the nanostructures. This technique is validated by comparison of the results to numerical simulations, where agreement is obtained, thereby confirming the near-field nature of the images. Our approach does not require any advanced equipment and we suggest that it could be applied to any type of sample, while keeping the measurement times reasonably short.

scholarly journals Coupling Methodology for Studying the Far Field Effects of Wave Energy Converter Arrays over a Varying Bathymetry

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2899 ◽  
Author(s):  
Gael Verao Fernandez ◽  
Philip Balitsky ◽  
Vasiliki Stratigaki ◽  
Peter Troch
Keyword(s):  
Numerical Simulations ◽  
Wave Energy ◽  
Near Field ◽  
Coupled Model ◽  
Propagation Model ◽  
Irregular Waves ◽  
Computational Time ◽  
Far Field ◽  
Field Effects ◽  
Numerical Tool

For renewable wave energy to operate at grid scale, large arrays of Wave Energy Converters (WECs) need to be deployed in the ocean. Due to the hydrodynamic interactions between the individual WECs of an array, the overall power absorption and surrounding wave field will be affected, both close to the WECs (near field effects) and at large distances from their location (far field effects). Therefore, it is essential to model both the near field and far field effects of WEC arrays. It is difficult, however, to model both effects using a single numerical model that offers the desired accuracy at a reasonable computational time. The objective of this paper is to present a generic coupling methodology that will allow to model both effects accurately. The presented coupling methodology is exemplified using the mild slope wave propagation model MILDwave and the Boundary Elements Methods (BEM) solver NEMOH. NEMOH is used to model the near field effects while MILDwave is used to model the WEC array far field effects. The information between the two models is transferred using a one-way coupling. The results of the NEMOH-MILDwave coupled model are compared to the results from using only NEMOH for various test cases in uniform water depth. Additionally, the NEMOH-MILDwave coupled model is validated against available experimental wave data for a 9-WEC array. The coupling methodology proves to be a reliable numerical tool as the results demonstrate a difference between the numerical simulations results smaller than 5% and between the numerical simulations results and the experimental data ranging from 3% to 11%. The simulations are subsequently extended for a varying bathymetry, which will affect the far field effects. As a result, our coupled model proves to be a suitable numerical tool for simulating far field effects of WEC arrays for regular and irregular waves over a varying bathymetry.

Improved Analytical Models for Single- and Multi-layer Silver Superlenses

2009 ◽  
Vol 1182 ◽  
Author(s):  
Ciaran P Moore ◽  
Richard John Blaikie ◽  
Matthew D Arnold
Keyword(s):  
Transfer Functions ◽  
Near Field ◽  
Single Layer ◽  
Analytical Models ◽  
Full Field ◽  
Accurate Performance ◽  
Imaging Performance ◽  
Performance Estimates ◽  
Continuous Metal ◽  
Good Agreement

AbstractSpatial-frequency transfer functions are regularly used to model the imaging performance of near-field �superlens� systems. However, these do not account for interactions between the object that is being imaged and the superlens itself. As the imaging in these systems is in the near field, such interactions are important to consider if accurate performance estimates are to be obtained. We present here a simple analytical modification that can be made to the transfer function to account for near-field interactions for objects consisting of small apertures in otherwise-continuous metal screens. The modified transfer functions are evaluated by comparison with full-field finite-element simulations for representative single-layer and multi-layer silver superlenses, and good agreement is found.

Calculation and Analysis of Near-Field Head-Related Transfer Functions from a Simplified Head-Neck-Torso Model

2012 ◽  
Vol 29 (3) ◽  
pp. 034302 ◽  
Author(s):  
Ze-Wei Chen ◽  
Guang-Zheng Yu ◽  
Bo-Sun Xie ◽  
Shan-Qun Guan
Keyword(s):  
Transfer Functions ◽  
Near Field ◽  
Torso Model ◽  
Head Neck

Near-Field Virtual Audio Displays

2002 ◽  
Vol 11 (1) ◽  
pp. 93-106 ◽  
Author(s):  
Douglas S. Brungart
Keyword(s):  
Transfer Functions ◽  
Near Field ◽  
Multimodal Interfaces ◽  
Sound Sources ◽  
Auditory Cues ◽  
Current State ◽  
Potential Applications ◽  
Technical Challenges ◽  
State Of Research ◽  
Virtual Audio

Although virtual audio displays are capable of realistically simulating relatively distant sound sources, they are not yet able to accurately reproduce the spatial auditory cues that occur when sound sources are located near the listener's head. Researchers have long recognized that the binaural difference cues that dominate auditory localization are independent of distance beyond 1 m but change systematically with distance when the source approaches with in 1 m of the listener's head. Recent research has shown that listeners are able to use these binaural cues to determine the distances of nearby sound sources. However, technical challenges in the collection and processing of near-field head-related transfer functions (HRTFs) have thus far prevented the construction of a fully functional near-field audio display. This paper summarizes the current state of research in the localization of nearby sound sources and outlines the technical challenges involved in the creation of a near-field virtual audio display. The potential applications of near-field displays in immersive virtual environments and multimodal interfaces are also discussed.

scholarly journals Substituting EMC emission measurement by field and cable scan method using measured transfer function

2013 ◽  
Vol 11 ◽  
pp. 183-188 ◽  
Author(s):  
D. Rinas ◽  
J. Jia ◽  
A. Zeichner ◽  
S. Frei
Keyword(s):  
Transfer Functions ◽  
Near Field ◽  
Good Alternative ◽  
Emission Measurement ◽  
Far Field ◽  
Field Calculation ◽  
Automotive Components ◽  
Anechoic Chambers ◽  
Cispr 25 ◽  
Space Requirements

Abstract. Today EMC emissions of automotive components are often measured in anechoic chambers by an antenna at fixed position according to CISPR 25 (ALSE-method). The antenna voltage often cannot sufficiently describe the behaviour of the measured electronic components and systems. Furthermore space requirements and costs are very high for the ALSE-method. Field- and cable-scan methods combined with near-field to far-field transformation techniques might be a good alternative. Residual reflections from the walls, the metallic floor, the measuring table, interaction of the antenna with the environment, and other factors affect the measurements. Thus, models which only regard the current distribution for near- and far field calculation cannot produce results equal to a chamber measurement. In this paper methods for computing transfer functions for the substitution of EMC antenna measurements with field- and cable scans in a specified calibration area are introduced. To consider influences of the environment, the environment is characterized in a first step and included with transfer functions in the calculation process for the equivalent ALSE-field.

Sign in / Sign up

Export Citation Format

Share Document