scholarly journals Location Fingerprint Extraction for Magnetic Field Magnitude Based Indoor Positioning

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
Wenhua Shao ◽  
Fang Zhao ◽  
Cong Wang ◽  
Haiyong Luo ◽  
Tunio Muhammad Zahid ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Feature Extraction ◽  
Measurement Technique ◽  
Extraction Methods ◽  
Indoor Positioning ◽  
Coarse Grained ◽  
Electronic Noise ◽  
Magnetic Field Magnitude ◽  
Positioning Method ◽  
The Magnetic Field

Smartphone based indoor positioning has greatly helped people in finding their positions in complex and unfamiliar buildings. One popular positioning method is by utilizing indoor magnetic field, because this feature is stable and infrastructure-free. In this method, the magnetometer embedded on the smartphone measures indoor magnetic field and queries its position. However, the environments of the magnetometer are rather harsh. This harshness mainly consists of coarse-grained hard/soft-iron calibrations and sensor electronic noise. The two kinds of interferences decrease the position distinguishability of the magnetic field. Therefore, it is important to extract location features from magnetic fields to reduce these interferences. This paper analyzes the main interference sources of the magnetometer embedded on the smartphone. In addition, we present a feature distinguishability measurement technique to evaluate the performance of different feature extraction methods. Experiments revealed that selected fingerprints will improve position distinguishability.

scholarly journals Indoor Positioning Using Magnetic Fingerprint Map Captured by Magnetic Sensor Array

Sensors ◽  
2021 ◽  
Vol 21 (17) ◽  
pp. 5707
Author(s):  
Ching-Han Chen ◽  
Pi-Wei Chen ◽  
Pi-Jhong Chen ◽  
Tzung-Hsin Liu
Keyword(s):  
Magnetic Field ◽  
Sensor Array ◽  
Probabilistic Neural Network ◽  
Indoor Positioning ◽  
Magnetic Sensor ◽  
Magnetic Sensors ◽  
Positioning System ◽  
Positioning Accuracy ◽  
Positioning Method ◽  
The Magnetic Field

By collecting the magnetic field information of each spatial point, we can build a magnetic field fingerprint map. When the user is positioning, the magnetic field measured by the sensor is matched with the magnetic field fingerprint map to identify the user’s location. However, since the magnetic field is easily affected by external magnetic fields and magnetic storms, which can lead to “local temporal-spatial variation”, it is difficult to construct a stable and accurate magnetic field fingerprint map for indoor positioning. This research proposes a new magnetic indoor positioning method, which combines a magnetic sensor array composed of three magnetic sensors and a recurrent probabilistic neural network (RPNN) to realize a high-precision indoor positioning system. The magnetic sensor array can detect subtle magnetic anomalies and spatial variations to improve the stability and accuracy of magnetic field fingerprint maps, and the RPNN model is built for recognizing magnetic field fingerprint. We implement an embedded magnetic sensor array positioning system, which is evaluated in an experimental environment. Our method can reduce the noise caused by the spatial-temporal variation of the magnetic field, thus greatly improving the indoor positioning accuracy, reaching an average positioning accuracy of 0.78 m.

scholarly journals Autofocus Entropy Repositioning Method Bioinspired in the Magnetic Field Memory of the Bees Applied to Pollination

Sensors ◽  
2021 ◽  
Vol 21 (18) ◽  
pp. 6198
Author(s):  
Daniel de Matos Luna dos Santos ◽  
Ewaldo Eder Carvalho Santana ◽  
Paulo Fernandes da Silva Junior ◽  
Jonathan Araujo Queiroz ◽  
João Viana da Fonseca Neto ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Feature Extraction ◽  
Real Time ◽  
Unsupervised Method ◽  
Color Characteristics ◽  
Magnetic Declination ◽  
Positioning Method ◽  
The Magnetic Field ◽  
Robust Response

In this paper, a bioinspired method in the magnetic field memory of the bees, applied in a rover of precision pollination, is presented. The method calculates sharpness features by entropy and variance of the Laplacian of images segmented by color in the HSV system in real-time. A complementary positioning method based on area feature extraction between active markers was developed, analyzing color characteristics, noise, and vibrations of the probe in time and frequency, through the lateral image of the probe. From the observed results, it can be seen that the unsupervised method does not require previous calibration of target dimensions, histogram, and distances involved in positioning. The algorithm showed less sensitivity in the extraction of sharpness characteristics regarding the number of edges and greater sensitivity to the gradient, allowing unforeseen operation scenarios, even in small sharpness variations, and robust response to variance local, temporal, and geophysical of the magnetic declination, not needing luminosity after scanning, with the two freedom of degrees of the rotation.

scholarly journals 3D Magneto-Buoyancy-Thermocapillary Convection of CNT-Water Nanofluid in the Presence of a Magnetic Field

Processes ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 258 ◽  
Author(s):  
Lioua Kolsi ◽  
Salem Algarni ◽  
Hussein A. Mohammed ◽  
Walid Hassen ◽  
Emtinene Lajnef ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Flow Structure ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Numerical Study ◽  
Flow Stabilization ◽  
Magnetic Field Magnitude ◽  
The Magnetic Field

A numerical study is performed to investigate the effects of adding Carbon Nano Tube (CNT) and applying a magnetic field in two directions (vertical and horizontal) on the 3D-thermo-capillary natural convection. The cavity is differentially heated with a free upper surface. Governing equations are solved using the finite volume method. Results are presented in term of flow structure, temperature field and rate of heat transfer. In fact, results revealed that the flow structure and heat transfer rate are considerably affected by the magnitude and the direction of the magnetic field, the presence of thermocapillary forces and by increasing nanoparticles volume fraction. In opposition, the increase of the magnetic field magnitude leads to the control the flow causing flow stabilization by merging vortexes and reducing heat transfer rate.

scholarly journals Multi-point observations of intermittency in the cusp regions

2007 ◽  
Vol 14 (4) ◽  
pp. 525-534 ◽  
Author(s):  
M. M. Echim ◽  
H. Lamy ◽  
T. Chang
Keyword(s):  
Magnetic Field ◽  
Magnetic Energy ◽  
Haar Wavelet ◽  
Distribution Functions ◽  
Statistical Properties ◽  
Coarse Grained ◽  
Haar Wavelet Transform ◽  
Intermittent Behavior ◽  
Field Fluctuations ◽  
The Magnetic Field

Abstract. In this paper we investigate the statistical properties of magnetic field fluctuations measured by the four Cluster spacecraft in the cusp and close to the interface with the magnetospheric lobes, magnetopause and magnetosheath. At lower altitudes along the outbound orbit of 26 February 2001, the magnetic field fluctuations recorded by all four spacecraft are random and their Probability Distribution Functions (PDFs) are Gaussian at all scales. The flatness parameter, F – related to the kurtosis of the time series, is equal to 3. At higher altitudes, in the cusp and its vicinity, closer to the interface with the magnetopause and magnetosheath, the PDFs from all Cluster satellites are non-Gaussian and show a clear intermittent behavior at scales smaller than τG≈ 61 s (or 170 km). The flatness parameter increases to values greater than 3 for scales smaller than τG. A Haar wavelet transform enables the identification of the "events" that produce sudden variations of the magnetic field and of the scales that have most of the power. The LIM parameter (i.e. normalized wavelet power) indicates that events for scales below 65 s are non-uniformly distributed throughout the cusp passage. PDFs, flatness and wavelet analysis show that at coarse-grained scales larger than τG the intermittency is absent in the cusp. Fluctuations of the magnetic energy observed during the same orbit in the magnetosheath show PDFs that tend toward a Gaussian at scales smaller than τG found in the cusp. The flatness analysis confirms the decreasing of τG from cusp to magnetosheath. Our analysis reveals the turbulent cusp as a transition region from a non-intermittent turbulent state inside the magnetosphere to an intermittent turbulent state in the magnetosheath that has statistical properties resembling the solar wind turbulence. The observed turbulent fluctuations in the cusp suggests a phenomenon of nonlinear interactions of plasma coherent structures as in contemporary models of space plasma turbulence.

scholarly journals Magnetic field disturbances in the sheath region of a super-sonic interplanetary magnetic cloud

2008 ◽  
Vol 26 (10) ◽  
pp. 3153-3158 ◽  
Author(s):  
E. Romashets ◽  
M. Vandas ◽  
S. Poedts
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Storms ◽  
Magnetic Cloud ◽  
The Body ◽  
Magnetic Clouds ◽  
Shock Surface ◽  
Sheath Region ◽  
Magnetic Field Magnitude ◽  
The Magnetic Field ◽  
Magnetic Disturbances

Abstract. It is well-known that interplanetary magnetic clouds can cause strong geomagnetic storms due to the high magnetic field magnitude in their interior, especially if there is a large negative Bz component present. In addition, the magnetic disturbances around such objects can play an important role in their "geo-effectiveness". On the other hand, the magnetic and flow fields in the CME sheath region in front of the body and in the rear of the cloud are important for understanding both the dynamics and the evolution of the interplanetary cloud. The "eventual" aim of this work is to calculate the magnetic field in this CME sheath region in order to evaluate the possible geo-efficiency of the cloud in terms of the maximum |Bz|-component in this region. In this paper we assess the potential of this approach by introducing a model with a simplified geometry. We describe the magnetic field between the CME shock surface and the cloud's boundary by means of a vector potential. We also apply our model and present the magnetic field distribution in the CME sheath region in front of the body and in the rear of the cloud formed after the event of 20 November 2003.

scholarly journals Cluster-C1 observations on the geometrical structure of linear magnetic holes in the solar wind at 1 AU

2010 ◽  
Vol 28 (9) ◽  
pp. 1695-1702 ◽  
Author(s):  
T. Xiao ◽  
Q. Q. Shi ◽  
T. L. Zhang ◽  
S. Y. Fu ◽  
L. Li ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Geometrical Structure ◽  
Occurrence Rate ◽  
Geometrical Shape ◽  
Magnetic Field Data ◽  
Magnetic Field Magnitude ◽  
The Relationship ◽  
Plasma Measurements ◽  
The Magnetic Field

Abstract. Interplanetary linear magnetic holes (LMHs) are structures in which the magnetic field magnitude decreases with little change in the field direction. They are a 10–30% subset of all interplanetary magnetic holes (MHs). Using magnetic field and plasma measurements obtained by Cluster-C1, we surveyed the LMHs in the solar wind at 1 AU. In total 567 interplanetary LMHs are identified from the magnetic field data when Cluster-C1 was in the solar wind from 2001 to 2004. We studied the relationship between the durations and the magnetic field orientations, as well as that of the scales and the field orientations of LMHs in the solar wind. It is found that the geometrical structure of the LMHs in the solar wind at 1 AU is consistent with rotational ellipsoid and the ratio of scales along and across the magnetic field is about 1.93:1. In other words, the structure is elongated along the magnetic field at 1 AU. The occurrence rate of LMHs in the solar wind at 1 AU is about 3.7 per day. It is shown that not only the occurrence rate but also the geometrical shape of interplanetary LMHs has no significant change from 0.72 AU to 1 AU in comparison with previous studies. It is thus inferred that most of interplanetary LMHs observed at 1 AU are formed and fully developed before 0.72 AU. The present results help us to study the formation mechanism of the LMHs in the solar wind.

First measurements of the Mesospheric Magnetic Field in the Auroral Zone by means of laser

2020 ◽  
Author(s):  
Magnar G. Johnsen ◽  
Njål Gulbrandsen ◽  
Paul Hillman ◽  
Craig Denman ◽  
Jürgen Matzka ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Time Scales ◽  
Optical Pumping ◽  
Sodium Atom ◽  
Auroral Zone ◽  
Geomagnetic Variations ◽  
Sum Frequency ◽  
Sodium Layer ◽  
Magnetic Field Magnitude ◽  
The Magnetic Field

<p>In December 2019, for the first time, we were able to remotely measure the magnetic field in the mesospheric sodium layer, in the auroral zone.</p><p>By means of laser optical pumping and Larmor-resonance detection, it is possible to use the naturally occurring sodium layer in the mesosphere to measure Earth’s magnetic field magnitude at 90 km above ground. This is an altitude otherwise only accessible by rockets, which only will provide point measurements of very short time scales.</p><p>During the winter of 2019-20 we have applied a cw sum-frequency fasor/laser for probing the sodium-atom Larmor resonance at the Artic Lidar Observatory for Mesospheric Research (ALOMAR) at Andøya in northern Norway in order to measure and monitor the magnetic field in situ in the high latitude mesosphere over longer time scales.</p><p>The technique, which has been proved earlier at mid-latitudes, has now been confirmed and applied to high latitudes in the auroral zone during disturbed auroral and geomagnetic conditions. The magnetic field in the auroral zone is close to vertical making our measurements a notable achievement since the beam is closer to parallel with the magnetic field, contary to earlier measurements being closer to perpendicular as shown as best by theory.</p><p>This opens up for a completely new domain of measurements of externally generated geomagnetic variations related to currents in the magnetosphere-ionosphere system.</p><p>Here we report on the instrumental setup, and discuss our measurements of the mesospheric magnetic field.</p>

Threshold speed for two-dimensional confinement of charged particles in certain axisymmetric magnetic fields

2018 ◽  
Vol 96 (5) ◽  
pp. 519-523 ◽  
Author(s):  
K. Kabin ◽  
G. Kalugin ◽  
E. Spanswick ◽  
E. Donovan
Keyword(s):  
Magnetic Field ◽  
Power Law ◽  
Critical Speed ◽  
Longitudinal Magnetic Field ◽  
Strong Dependence ◽  
Charged Particles ◽  
Transcendental Equation ◽  
Power Exponent ◽  
Magnetic Field Magnitude ◽  
The Magnetic Field

In this paper we discuss conditions under which charged particles are confined by an axisymmetric longitudinal magnetic field with power law dependence on the radius. We derive a transcendental equation for the critical speed corresponding to the threshold between bounded and unbounded trajectories of the particles. This threshold speed shows strong dependence on the direction, and this dependence becomes more prominent as the exponent of the power law increases. The equation for threshold speed can be solved exactly for several specific values of the power exponent, but in general it requires a numerical treatment. Remarkably, if the magnetic field magnitude decreases more slowly than the inverse of the radius, charged particles remain confined no matter how large their energies may be.

scholarly journals SHEAR STRESS MEASUREMENTS AT THE SEA BOTTOM BY MEANS OF FERROFLUIDS

2018 ◽  
pp. 88
Author(s):  
Antonino Viviano ◽  
Laura M. Stancanelli ◽  
Rosaria E. Musumeci ◽  
Enrico Foti
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Measurement Technique ◽  
Fixed Bed ◽  
Optical Readout ◽  
Experimental Campaign ◽  
Sea Bottom ◽  
Sensor Configuration ◽  
Bed Roughness ◽  
The Magnetic Field

An innovative measurement technique is proposed for investigating shear stress at sandy bottoms. This technique is based on the adoption of a ferrofluidic sensor and of an optical readout strategy. An experimental campaign is carried out for evaluating its performance. Experiments differ for the ferrofluidic sensor configuration (difference in the magnetic field) and for the bottom configurations (fixed bed or sandy bed). Calibration of the ferrofluidic sensor for the range of the investigated hydraulic condition and of the controlling magnetic field is presented. The ferrofluidic technique is promising when applied at sandy bottoms, as neither adhesion processes between sand grains and ferrofluid or influence of impacts of grains on the measurement are observed. In particular, the preliminary measure performed indicated that the ferrofluidic sensor is capable of sensing the different bed roughness.

scholarly journals A Solar Source of Alfvénic Magnetic Field Switchbacks: In Situ Remnants of Magnetic Funnels on Supergranulation Scales

2021 ◽  
Vol 923 (2) ◽  
pp. 174
Author(s):  
S. D. Bale ◽  
T. S. Horbury ◽  
M. Velli ◽  
M. I. Desai ◽  
J. S. Halekas ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Leading Edge ◽  
Alpha Particles ◽  
Pressure Balance ◽  
Radial Magnetic Field ◽  
Solar Transition Region ◽  
Solar Transition ◽  
Magnetic Field Magnitude ◽  
Suprathermal Ions ◽  
The Magnetic Field

Abstract One of the striking observations from the Parker Solar Probe (PSP) spacecraft is the prevalence in the inner heliosphere of large amplitude, Alfvénic magnetic field reversals termed switchbacks. These δ B R / B ∼  ( 1 ) fluctuations occur over a range of timescales and in patches separated by intervals of quiet, radial magnetic field. We use measurements from PSP to demonstrate that patches of switchbacks are localized within the extensions of plasma structures originating at the base of the corona. These structures are characterized by an increase in alpha particle abundance, Mach number, plasma β and pressure, and by depletions in the magnetic field magnitude and electron temperature. These intervals are in pressure balance, implying stationary spatial structure, and the field depressions are consistent with overexpanded flux tubes. The structures are asymmetric in Carrington longitude with a steeper leading edge and a small (∼1°) edge of hotter plasma and enhanced magnetic field fluctuations. Some structures contain suprathermal ions to ∼85 keV that we argue are the energetic tail of the solar wind alpha population. The structures are separated in longitude by angular scales associated with supergranulation. This suggests that these switchbacks originate near the leading edge of the diverging magnetic field funnels associated with the network magnetic field—the primary wind sources. We propose an origin of the magnetic field switchbacks, hot plasma and suprathermals, alpha particles in interchange reconnection events just above the solar transition region and our measurements represent the extended regions of a turbulent outflow exhaust.

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