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Burlington, MA, United States

Fontes E.,Comsol Inc.
Chemical Engineering Progress | Year: 2015

Models can be used to describe chemical reactors to help solve problems and optimize processes, while saving time, money, and resources. Mathematical modeling of chemical reactors is based on fundamental conservation laws. When these laws are combined with equations based on constitutive relations, thermodynamics, and reaction kinetics, the model?s solutions are able to describe the composition, temperature, and pressure inside a chemical reactor. Kinetic and thermodynamic equations could be used to describe the diffusivity and the reaction term. In computer models, time and space can be discretized by elements to generate a numerical model with a high resolution. Models are validated to check that they are able to describe the real system. The validation can be both qualitative and quantitative. If a qualitative validation shows that the model describes the real reactor, quantitative validation can be performed based on parameter estimation. Source

Segui J.A.,Comsol Inc.
Solid State Technology | Year: 2013

The electrochemical etching of silicon in HF represents a versatile process that depends on many variables. The use of multiphysics simulation to investigate the impact of process variables will lead to a viable commercial process that is relevant for a range of substrate types and applications. This article is based on an article by A. Ivanov and U. Mescheder, "Dynamic Simulation of Electrochemical Etching of Silicon with lg COMSOL," presented at the COMSOL Conference 2012, October 10-12, 2012, Milan, Italy. Source

Yahiaoui R.,CNRS XLIM Research Institute, Limoges | Strikwerda A.C.,Comsol Inc. | Jepsen P.U.,Technical University of Denmark
IEEE Sensors Journal | Year: 2016

We have designed, fabricated, and experimentally verified a highly sensitive plasmonic sensing device in the terahertz frequency range. For a proof of concept of the sensing phenomenon, we have chosen the so-called fishnet structure based on circular hole array insensitive to the polarization of the incident wave. We employ the localized resonance associated with the cutoff frequency (electric plasma frequency) of the hole array to investigate its sensing capability. A thin-film overlayer deposited on the surface of the metallic apertures causes an amplitude modulation and a shift in the resonant frequency of the terahertz transmission. The frequency shift and the amplitude modulation were investigated as a function of the refractive index and the thickness of the overlayer for determining the sensing potential of the proposed structure. Measurements carried out using terahertz time-domain spectroscopy show good agreement with the numerical predictions. The results we obtained indicate that the proposed device could be very promising for enhancing the sensing capabilities of the refractive index changes involved in bio-applications, for instance. © 2016 IEEE. Source

Foley A.,Comsol Inc.
Microwave Journal | Year: 2013

A team from the Cross Cancer Institute in Edmonton, Canada has found a way to combine the two systems, MRI and Linac. The first step in designing the Linac-MR was mitigating the electromagnetic interactions that take place between the linac and MR scanner, a process that requires an in-depth understanding of how one system affects the performance of the other. A linac, on the other hand, uses an RF waveguide to create an oscillating electromagnetic (EM) field that accelerates an electron beam toward a target, thereby producing the x-rays used to destroy tumor cells. The program works by taking several images per second during treatment, and then auto-contouring the images using an in-house software that determines the tumors shape and position. The accuracy of the motion-prediction software was determined using an MR tractable 'phantom' that was representative of a tumor. The Linac-MR prototype is currently undergoing its final tests, and the team is preparing the documentation required to seek governmental approval for the device to be used in clinical trials. Source

Grahn P.,Comsol Inc. | Annila A.,University of Helsinki | Kolehmainen E.,University of Jyvaskyla
AIP Advances | Year: 2016

Recent reports about propulsion without reaction mass have been met on one hand with enthusiasm and on the other hand with some doubts. Namely, closed metal cavities, when fueled with microwaves, have delivered thrust that could eventually maintain satellites on orbits using solar power. However, the measured thrust appears to be without any apparent exhaust. Thus the Law of Action-Reaction seems to have been violated. We consider the possibility that the exhaust is in a form that has so far escaped both experimental detection and theoretical attention. In the thruster's cavity microwaves interfere with each other and invariably some photons will also end up co-propagating with opposite phases. At the destructive interference electromagnetic fields cancel. However, the photons themselves do not vanish for nothing but continue in propagation. These photon pairs without net electromagnetic field do not reflect back from the metal walls but escape from the resonator. By this action momentum is lost from the cavity which, according to the conservation of momentum, gives rise to an equal and opposite reaction. We examine theoretical corollaries and practical concerns that follow from the paired-photon conclusion. © 2016 Author(s). Source

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