This paper presents a simple, compact, and low-power method for generating extremely low-frequency radio signals below ~500 Hz. This paper is motivated by the prohibitively large size and low ...efficiency of conventional antennas operating in this frequency range. The successful generation of time-varying magnetic fields produced by the physical rotation of a 3 cm 3 permanent magnet is demonstrated. Ground plane and receiver orientation effects are analyzed both theoretically and experimentally. Observations as a function of distance from the source indicate that the fields are dominated by the static component, rather than by the radiation component, of the generated field. Based on these observations, the electromagnetic radiation emitted by a spinning magnet source is predicted to be weak. Nevertheless, static magnetic signaling using this technique is proven to be both possible and practical at frequencies below ~500 Hz and at distances in excess of 100 m.
•A novelty analytical 3D wake model is proposed.•The wind shear effect and the anisotropic wake expansion rate are studied.•Field measurements are conducted using LiDARs.•The 3D model is validated by ...LiDARs measured data.•The 3D model has good performance in predicting the wake profiles.
To further investigate the three-dimensional wake profiles for horizontal-axis wind turbines, a three-dimensional Jensen-Gaussian (3DJG) wake model is proposed and validated using field measurement data. The proposed 3DJG model takes the wind shear effect into account and considers the wind speed difference between wind shear inflow and uniform inflow. In addition, the influence of turbulence intensity in wake region on anisotropic wake expansion rate k is also modified. Different from previous ones, this model does not need multiple trial calculations to determine some empirical parameters, such as the wake expansion rate k when predicting the wake profile. The value of k is assigned based on the incoming wind conditions firstly and followed by the wake profile predictions. Performance of the newly proposed 3DJG model is compared and validated with previous models as well as the field measurement data. The corresponding experiment using two ground-based scanning LiDARs was conducted to detect the 3D wake characteristics of horizontal-axis wind turbines in a wind farm located in northern Hebei Province, China. Results show that the 3DJG model has higher accuracies in both horizontal plane and vertical height direction in the prediction of wake profiles. Guidelines for the quantification of turbines’ wake characteristics and model modifications can be provided by this study.
Full‐field optical measurements like digital image correlation or the grid method have brought a paradigm shift in the experimental mechanics community. While inverse identification techniques like ...finite element model updating or the virtual fields method have been the object of significant developments, current test methods, inherited from the age of strain gauges or linear variable displacement transducers, are generally not well adapted to the rich information provided by these new measurement tools. This paper provides a review of the research dealing with the design and optimization of heterogeneous mechanical tests for the identification of material parameters from full‐field measurements, christened here Material Testing 2.0 (MT2.0).
This article presents a defect detection method for diagnosing pseudo soldering problems in radio frequency (RF) circuit components. The algorithm integrates the source reconstruction method with the ...difference method (DM-SRM) to reconstruct the source distribution pinpointing the defect location effectively. Initially, the algorithm utilizes the difference between the radiated fields of the intact device and the defective one as input for the SRM. Subsequently, leveraging prior information regarding the sparsity of defects, the algorithm utilizes elastic regularization to address the ill-conditioned problems inherent in the SRM, thereby enhancing its noise robustness. The proposed method's effectiveness and robustness are demonstrated through simulations on patch antennas and measurements using a near-field system for a microstrip power divider and a low-noise amplifier (LNA).
A simple miniature magnetic-field probe for near-field measurements in 9-kHz-20-GHz bandwidth, which is applied to highspeed circuits, has been proposed and manufactured. The magneticfield probe is ...built on a four-layer printed circuit board (PCB) using high-performance and low-loss Rogers material (ε r = 3.48 and tan δ = 0.0037). Electric field coupling can be suppressed by PCB shielding structure of the magnetic-field probe. Coax-thru-hole via array technique is used to achieve impedance match. The resonance in working frequency band is suppressed through via fence, making |S 21 | rather smooth in the operation band. Experimental results show that the working frequency band is up to 9 kHz-20 GHz.
Magnetic Maps for Indoor Navigation Gozick, B.; Subbu, K. P.; Dantu, R. ...
IEEE transactions on instrumentation and measurement,
2011-Dec., 2011-12-00, 20111201, Letnik:
60, Številka:
12
Journal Article
Recenzirano
Magnetic field fluctuations and anomalies inside buildings tend to have a great effect on the compass, which is one of the simplest navigation devices. Alternative navigation requires landmark ...identification, so those landmarks can be used as guideposts in assisting individuals. By employing a mobile phone with built_in magnetometer, an extensive data set of 2000 measurements was collected. Using these fields, we identify landmarks and guideposts and create magnetic maps for multiple corridors of a floor in a building. Different phones are used at different sensitivity rates, which effectively portray similar results. Magnetic signatures are used for identifying locations and rooms and are independent of the person, the phone, and the sensitivity of the sensor being used. Magnetic field behavior is demonstrated and compared with theoretical distributions of these fields. The developed magnetic maps can complement existing visual maps for location tracking and navigation of autonomous robots indoors. These maps are particularly useful during limited visual feedback in poor lighting conditions. Moreover, building designers could include this landmark and guidepost information when developing the architecture of a building, which could in turn help people or robots navigate during disasters and emergency evacuations.
This review focuses on the observed characteristics of atmospheric new particle formation (NPF) in different environments of the global troposphere. After a short introduction, we will present a ...theoretical background that discusses the methods used to analyze measurement data on atmospheric NPF and the associated terminology. We will update on our current understanding of regional NPF, i.e. NPF taking simultaneously place over large spatial scales, and complement that with a full review on reported NPF and growth rates during regional NPF events. We will shortly review atmospheric NPF taking place at sub-regional scales. Since the growth of newly-formed particles into larger sizes is of great current interest, we will briefly discuss our observation-based understanding on which gaseous compounds contribute to the growth of newly-formed particles, and what implications this will have on atmospheric cloud condensation nuclei formation. We will finish the review with a summary of our main findings and future outlook that outlines the remaining research questions and needs for additional measurements.
The Van Allen Probes spacecraft flew through the inner radiation belt and the plasmasphere, probing the extremely dynamic coupling between the thermosphere, the ionosphere and the subauroral ...magnetosphere. Examining the electrodynamics of this region using Van Allen Probes data required that the ∼1 mV/m electric field (E‐field) of interest be measured in a region where the E‐field due to spacecraft motion was ∼100 mV/m. This means that the E‐field, the magnetic field, and the spacecraft velocity had to be measured to better than 1%. The instruments on board the Van Allen Probes have achieved this accuracy, delivering reliable near equatorial E‐field measurements even below three Earth radii. The objective of this commentary is to summarize the methodology developed over the years to maximize the accuracy and scientific return of these double probe E‐field measurements below L = 3.
Key Points
Van Allen Probes E‐field measurements are reliable even below three Earth radii
The data processing leverages the high accuracy of spin‐plane double probe E‐field measurements
The data processing relies on the assumption of no E‐field component parallel to the magnetic field direction
With the advent of camera‐based full‐field measurement techniques such as digital image correlation (DIC), researchers have been trying to exploit such rich data sets through the use of more complex ...test configurations than the standard ones (uniaxial tension/compression, bending etc.). This new paradigm in mechanical testing of materials has recently been christened ‘Material Testing 2.0’. This paper provides a brief overview of this field, which is currently seeing a large increase in research effort.
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