scholarly journals Spherical harmonic based noise rejection and neuronal sampling with multi-axis OPMs

2021 ◽  
Author(s):  
Tim M Tierney ◽  
Stephanie Mellor ◽  
George C O'Neill ◽  
Ryan C Timms ◽  
Gareth R Barnes
Keyword(s):  
Degrees Of Freedom ◽  
External Noise ◽  
Interference Rejection ◽  
Optically Pumped ◽  
Vector Spherical Harmonics ◽  
Noise Rejection ◽  
Neuronal Signal ◽  
Very High ◽  
Spatial Degrees Of Freedom ◽  
Irregular Solid Harmonics

In this study we explore the interference rejection and spatial sampling properties of multi-axis Optically Pumped Magnetometer (OPM) data. We use both vector spherical harmonics and eigenspectra to quantify how well an array can separate neuronal signal from environmental interference while adequately sampling the entire cortex. We found that triaxial OPMs have superb noise rejection properties allowing for very high orders of interference (L=6) to be accounted for while minimally affecting the neural space (2dB attenuation for a 60-sensor triaxial system). To adequately model the signals arising from the cortex, we show that at least 11th order (143 spatial degrees of freedom) irregular solid harmonics or 95 eigenvectors of the lead field are needed to model the neural space for OPM data (regardless of number of axes measured). This can be adequately sampled with 75-100 equidistant triaxial sensors (225-300 channels) or 200 equidistant radial channels. In other words, ordering the same number of channels in triaxial (rather than purely radial) configuration gives significant advantages not only in terms of external noise rejection but also minimizes cost, weight and cross-talk.

Design and Testing Outline for a Free Running Model of a High Speed Craft

2020 ◽  
Author(s):  
Xinguo Wang ◽  
Jack Bonoli ◽  
Madeline Cohen ◽  
Mirjam Fürth
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Six Degrees Of Freedom ◽  
High Interest ◽  
Outdoor Environments ◽  
Free Running ◽  
Industry Professionals ◽  
Design And Testing ◽  
Very High ◽  
Testing Plan

Hydrodynamics of High Speed Craft is a topic of very high interest for recreational boaters and industry professionals alike. This project aims to be a first step toward conducting such experiments in exposed outdoor environments. This paper will outline a preliminary design and testing plan of a free running model of a high speed craft. The proposed free running model will be subjected to all six degrees of freedom, self propelled, autonomously controlled, and will be exposed to weather elements.

The Motion of the Human Center of Mass and its Relationship to Mechanical Impedance

1966 ◽  
Vol 8 (5) ◽  
pp. 399-405 ◽  
Author(s):  
Edmund B. Weis ◽  
Frank P. Primiano
Keyword(s):  
Transfer Function ◽  
Mechanical System ◽  
Degrees Of Freedom ◽  
Center Of Mass ◽  
Mechanical Impedance ◽  
Second Order ◽  
Analysis Tool ◽  
Isotropic Theory ◽  
Spatial Degrees Of Freedom

This report concerns the development of a relationship between the human mechanical impedance and the coupling of the human center of mass to the environment. The mechanical impedance is a common analysis tool in biomechanics while the analysis of the coupling of the center of mass to the environment is technically more difficult, if not impossible. The development is based on linear, passive, isotropic theory and shows that the transfer function which expresses the relation between the motion of the center of mass and the motion of the source is similar to a linear second order mechanical system in each of the translational spatial degrees of freedom.

Continuum Modeling of a Slewing ISAT (Innovative Space Antenna Technology)

2005 ◽  
Author(s):  
Armaghan Salehian ◽  
Eugene M. Cliff ◽  
Daniel J. Inman
Keyword(s):  
Continuum Model ◽  
Degrees Of Freedom ◽  
Natural Frequencies ◽  
Space Antenna ◽  
Geometrical Properties ◽  
Strain Components ◽  
Equivalent Continuum Model ◽  
Equivalent Continuum ◽  
Very High ◽  
The Continuum

A simple approach is presented herein for obtaining the equivalent continuum model of an ISAT (Innovative Space Antenna Technology) truss structure in order to find the free vibration solutions for different coordinates of vibration. Kinetic and potential energy expressions are written in terms of the strain components of the elements and the nodal velocities. The Lagrangian approach is employed to find the governing partial differential equations of the structure which for the bending degrees of freedom lead to an equivalent Timoshenko beam. Finally, the physical characteristics of the continuum model are written in terms of the material and geometrical properties of the truss, which provide a simple tool for comparing dynamic characteristics of lattices with different properties. The natural frequencies are found for each of the bending, longitudinal, and torsional coordinates of vibration and are compared to those of a FEM solution for the purpose of validation. The analytical model shows very high accuracy in prediction of the natural frequencies of the original truss.

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