18 research outputs found
Observation of Locally Negative Velocity of the Electromagnetic Field in Free Space
No full textSince the 1983 definition of the speed of light in vacuum as a fundamental constant with the exact value of 299 792 458 m/s the question has remained as to what apart from the wave front travels at that speed. It is commonly assumed that the entire electromagnetic waveform in free space does. Here it is demonstrated, both theoretically and experimentally, that the near- and intermediate-field dynamics of the vectorial electromagnetic field is much more complex than simple outwards propagation. In particular, it is shown that there exists a region close to the source, where, while the wave front travels outwards at the speed of light, the main body of the waveform appears to go inwards or back in time. The same effect may also lead to apparent superluminal results in free space.TelecommunicationsElectrical Engineering, Mathematics and Computer Scienc
Singular modes of the electromagnetic field
No full textElectrical Engineering, Mathematics and Computer Scienc
Superluminal, Subluminal, and Negative Velocities in Free-Space Electromagnetic Propagation
No full textLarge-Scale H<sub>2</sub> Optimization for Thermo-Mechanical Reliability of Electronics
No full textOptimization of transient models is required in several domains related to thermo-mechanical reliability of electronics, such as Prognostic Health Monitoring (PHM) and design optimization. A novel framework for efficient (local) parameter optimization of transient models in the H2 norm is proposed. The optimization is feasible for large-scale transient models because it approximates the gradient using physics-based model order reduction (MOR), in contrast to existing approaches that typically use data-driven surrogate models such as neural networks. To demonstrate the framework an optimal fixed-order virtual sensor for PHM of a Ball Grid Array (BGA) is numerically determined.</p
