## Global Modeling of a Non-Maxwellian Discharge in COMSOL®

##### Jose Gregorio November 19, 2018

Global modeling of plasmas is a powerful approach to study large chemistry sets. In these models, the reactions are represented by rate coefficients. In particular, the rate coefficients of electron impact collisions depend on the electron energy distribution function (EEDF), which is often non-Mawellian and can be computed from an approximation of the Boltzmann equation (BE). Here, we explain how to create a global model fully coupled with the BE in the two-term approximation using the COMSOL Multiphysics® software.

Lire la Suite##### Christopher Boucher November 5, 2018

Modern optical systems are often required to operate in harsh environments, including high altitudes, space, underwater, and in laser and nuclear facilities. Such optical systems are subjected to structural loads and extreme temperatures. The most accurate way to fully capture these environmental effects is through numerical simulation via a structural-thermal-optical performance (STOP) analysis. STOP analysis is the quintessential multiphysics problem. In this blog post, we show how to combine structural, thermal, and optical effects using the COMSOL Multiphysics® software.

Lire la Suite##### Brianne Christopher October 30, 2018

Is the boundary element method (BEM) a viable alternative to FEM for magnetostatics modeling? In a three-part series of tutorials, we perform electromagnetic force calculations using the Maxwell stress tensor to demonstrate the capabilities of BEM. The results are validated against analytical models and compared with results from FEM to show the value and utility of boundary elements for this purpose. Read on for a preview of what you’ll learn in the tutorial series.

Lire la Suite##### Chien Liu October 29, 2018

The effect of quantum tunneling can be important if the thickness of the energy barrier for the charge carrier is comparable to or smaller than the evanescent decay length. In order to account for this effect, we can use the WKB Tunneling Model feature, available in the Semiconductor Module as of version 5.4 of the COMSOL® software, for the heterojunction and Schottky contact boundary conditions. Here, we demonstrate their usage using a benchmark model.

Lire la Suite##### Bridget Paulus October 25, 2018

From tiny cellphone chargers to large-scale generators, transformers are used to increase, decrease, and isolate voltages in all sorts of applications. While these electrical devices have a pretty simple structure, optimizing their performance can be challenging, as it involves accounting for the coupling of magnetic and electric fields, the behavior of ferromagnetic materials, and more. To analyze these effects, engineers designing transformers can use the COMSOL® software.

Lire la Suite##### Thomas Forrister October 24, 2018

During routine exams, eye care professionals look for common refractive errors like nearsightedness, farsightedness, and astigmatism. As patients age, doctors also look for presbyopia, a loss of the accommodative amplitude that results long-term in a complete loss of the near vision. The visual accommodation process is complex, and useful eye properties needed to improve diagnosis and presbyopia treatment are difficult to obtain. To address the problem of measuring the refractive index of the lens, researchers developed a reverse engineering technique […]

Lire la Suite##### Walter Frei October 22, 2018

One of the core strengths of the COMSOL Multiphysics® software is the ability to easily define loads and constraints that move over time. There are actually several different ways in which this can be done, all within the core functionality of the software. In today’s blog post, we will guide you through three of these approaches.

Lire la Suite##### Chien Liu October 18, 2018

The Schrödinger-Poisson Equation multiphysics interface simulates systems with quantum-confined charge carriers, such as quantum wells, wires, and dots. Here, we examine a benchmark model of a GaAs nanowire to demonstrate how to use this feature in the Semiconductor Module, an add-on product to the COMSOL Multiphysics® software.

Lire la Suite##### Lipeng Liu October 12, 2018

Using the Numeric Port feature, available in the COMSOL Multiphysics® software with the add-on RF Module, the mode of a port with an arbitrary shape can be computed numerically via a boundary mode analysis. By adding a Frequency Domain or an Adaptive Frequency Sweep study, the S-Parameter and Smith plots can be obtained. The numeric port also enables us to calculate the characteristic impedance of transmission lines operating in the transverse electromagnetic (TEM) mode.

Lire la Suite##### Jiyoun Munn September 25, 2018

When we analyze high-frequency electromagnetics problems using the finite element method (FEM), we often compute S-parameters in the frequency domain without reviewing the results in the complementary domain; that is, the time domain. The time domain is where we can find other useful information, such as time-domain reflectometry (TDR). In this blog post, we will demonstrate data conversion between two domains in order to efficiently obtain results in the desired computation domain through a fast Fourier transform (FFT) process.

Lire la Suite##### Thomas Forrister September 13, 2018

With the rise of 5G and other wireless millimeter-wave applications, there has been an increase in front-end antenna solutions that depend on monopole, dipole, and patch antennas. In these devices, the radiation efficiency tends to suffer due to the effect of lossy silicon substrate materials. Enter the dielectric resonator: Antennas using these resonators (made of nonmetallic materials) have a higher radiation efficiency. To increase directivity and gain at high frequencies, engineers can optimize dielectric resonator antenna (DRA) designs with simulation.

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