IEEE journal on multiscale and multiphysics computational techniques 

About: IEEE journal on multiscale and multiphysics computational techniques is an academic journal published by Institute of Electrical and Electronics Engineers. The journal publishes majorly in the area(s): Computer science & Engineering. It has an ISSN identifier of 2379-8793. Over the lifetime, 62 publications have been published receiving 46 citations. The journal is also known as: JMMCT & Journal of multiscale and multiphysics computational techniques.

Semi-Analytical Model Using the Uniform Theory of Diffraction for Single Feed High Gain Antenna Structure

Abstract: The recent advancement in commercial electromagnetic computational solvers, along with the computational processing resources gives a huge advantage for antenna designers to study complex structures and optimize their performance. In addition, the huge leap in processors speeds, and the advent of parallel processing techniques made it possible to reduce the computation time dramatically. Consequently, this made it less attractive for designers to explore fast analytical models for their structures. The main drawback of the full and blind dependence on commercial solvers in the design process is the lack of the physical insight for the operating mechanism of the structure. On the other hand, despite that numerical and analytical series solutions can give an accurate solution to the electromagnetic problem being studied, they hardly can give an insight on the internal interactions and the operating mechanism of the structure. In this work we provide a semi-analytical model along with a thorough physical insight for a single feed high gain antenna structure. The provided model not only gives a powerful insight into understanding the radiation mechanism, but also is very computationally effective, and allows the use of antenna theory intuition, where the structure can be perceived as an antenna array, and the principles of array factor, power tapering, etc. can be intuitively used to understand and manipulate the structure radiation behavior.

Incident Plane-Wave Source Formulations for Leapfrog Complying-Divergence Implicit FDTD Method

Abstract: The commonly used unconditionally stable finite-difference time-domain (FDTD) methods such as alternating direction implicit (ADI)-FDTD, and its one-step formulation, leapfrog ADI-FDTD, have been found to violate the divergence condition of Gauss's law. The recently proposed leapfrog complying-divergence implicit (CDI)-FDTD not only addresses this problem, but also features many advantages, including unconditional stability, minimal floating-point operations and one-step leapfrog update. To further expand its application, this paper presents the incident plane-wave source formulations for leapfrog CDI-FDTD. Two stable and efficient formulations with different advantages are presented for introducing the far-zone plane-wave source into the FDTD problem space, namely, the scattered-field (SF) formulation and total-field / scattered field (TF/SF) formulation. To deal with the discontinuity and inconsistency across TF/SF boundaries, the fields on the boundaries need special treatments with careful modifications to ensure stability and proper plane-wave injection. Numerical results show that the incident fields can be effectively injected into the problem space with the stability of leapfrog CDI-FDTD maintained in both formulations. In addition, comparisons of radar cross sections computed using leapfrog CDI-FDTD, leapfrog ADI-FDTD and explicit FDTD with both SF and TF/SF formulations are presented. These demonstrate the advantages of leapfrog CDI-FDTD method in solving far-zone plane-wave source problems, including high efficiency, unconditional stability and complying divergence.

Full-Wave Methodology to Compute the Spontaneous Emission Rate of a Transmon Qubit

Abstract: The spontaneous emission rate (SER) is an important figure of merit for any quantum bit (qubit), as it can play a significant role in the control and decoherence of the qubit. As a result, accurately characterizing the SER for practical devices is an important step in the design of quantum information processing devices. Here, we specifically focus on the experimentally popular platform of a transmon qubit, which is a kind of superconducting circuit qubit. Despite the importance of understanding the SER of these qubits, it is often determined using approximate circuit models or is inferred from measurements on a fabricated device. To improve the accuracy of predictions in the design process, it is better to use full-wave numerical methods that can make a minimal number of approximations in the description of practical systems. In this work, we show how this can be done with a recently developed field-based description of transmon qubits coupled to an electromagnetic environment. We validate our model by computing the SER for devices similar to those found in the literature that have been well-characterized experimentally. We further cross-validate our results by comparing them to simplified lumped element circuit and transmission line models as appropriate.

Simulation of Surface Enhanced Raman Scattering From Nanoparticles With Wideband Nested Equivalence Source Approximation

Abstract: Surface Enhanced Raman Scattering (SERS) has been widely used in the fields of surface science, spectral analysis, biosensors, and biomedical detection. A wideband nested equivalent source approximation (WNESA) accelerated method of moments (MoM) of multiple material regions is proposed, for the analysis of SERS by nanostructure. The SERS affected by the diameter and distance between gold nanospheres for dimer structure is studied through numerical simulations with WNESA. It is found that nanoparticles-based SERS substrates with different dimensions and distances will produce different excitation wavelengths and SERS enhancement factors, by evaluating the variation of hot spot positions with wavelengths. The computational complexity of WNESA for SERS substrate simulation is O(N log N), where N is the number of unknowns. Significant improvement of the design efficiency of nanostructures for increasing the magnitude of SERS can be achieved.

Fourier Transform, Dirac Commutator, Energy Conservation, and Correspondence Principle for Electrical Engineers

Abstract: The canonical commutation relation is a fundamental postulate of the quantum theory regarding the operators needed in quantum description of physical observables. It is shown that the Fourier transform is derivable from this seemingly simple postulate along with the basic properties of the position and momentum operators. Further discussions on the canonical commutation relation reveal its connection to a more fundamental notion that energy must be conserved. This discussion also unveils the mathematical homomorphism between the classical and quantum theories for systems represented by sum separable Hamiltonians. Another link between the classical and quantum theories is established by the correspondence principle which states that the classical theory emerges from quantum theory in the limit of vanishingly small Planck constant. Finally, the quantum Maxwell’s equations, which have been derived in our previous works, are presented and briefly discussed, and the 3-D mode transform is derived that can be interpreted as a generalization of the Fourier transform. We present both the details and meanings of the 3-D mode transform which will serve as a foundation for a full 3-D quantum finite-difference time-domain method.