This study aimed to verify the possibility of stabilizing and focusing a plasma column generated by a plasma cutter. The simulation performed by the COMSOL Multiphysics software is based on the actual configuration and geometry of the burner. This article presented a universal computational method based on FEM simulations, focusing on the deflection of the current of electrically charged particles in a magnetic field within the context of a plasma cutting torch. The simulations estimate the optimal shape and positioning of a focused electron beam for various magnetic lens positions and plasma stream energies, revealing that higher initial electron energies lead to a more even beam focus. Among the configurations tested, positioning the cathode 3 mm above the ring-shaped permanent magnet proved most effective, maintaining beam linearity and minimizing electron scattering, making it suitable for practical implementations.

• Keywords
• cutting torch, magnetic focusing, microscopes, plasma arc, simulation software,
• Publication type
• Journal Article MeSH

This study presents the experimental and theoretical modeling results of pressure changes caused by fluid flow in a water aspirator (water pump) whose working principle is based on the Venturi effect. Experimentally measured pressure drop in a glass-made device is modeled in COMSOL Multiphysics by previously reproducing the device geometry. Computations were performed using a Fluid Flow Module with turbulence model RANS k-ε. Pressure and liquid velocity magnitude maps were drowned, and selected vertical and perpendicular cross-sections of velocity and pressure fields were shown and discussed, indicating model limitations.

• Keywords
• COMSOL, Finite element method, Turbulent flow, Venturi effect, Water pump,
• Publication type
• Journal Article MeSH

Objective.Producing realistic numerical models of neurostimulation electrodes in contact with the electrolyte and tissue, for use in time-domain finite element method simulations while maintaining a reasonable computational burden remains a challenge. We aim to provide a straightforward experimental-theoretical hybrid approach for common electrode materials (Ti, TiN, ITO, Au, Pt, IrOx) that are relevant to the research field of bioelectronics, along with all the information necessary to replicate our approach in arbitrary geometry for real-life experimental applications.Approach.We used electrochemical impedance spectroscopy (EIS) to extract the electrode parameters in the AC regime under different DC biases. The pulsed electrode response was obtained by fast amperometry (FA) to optimize and verify the previously obtained electrode parameters in a COMSOL Multiphysics model. For optimization of the electrode parameters a constant phase element (CPE) needed to be implemented in time-domain.Main results.We find that the parameters obtained by EIS can be used to accurately simulate pulsed response only close to the electrode open circuit potential, while at other potentials we give corrections to the obtained parameters, based on FA measurements. We also find that for many electrodes (Au, TiN, Pt, and IrOx), it is important to implement a distributed CPE rather than an ideal capacitor for estimating the electrode double-layer capacitance. We outline and provide examples for the novel time-domain implementation of the CPE for finite element method simulations in COMSOL Multiphysics.Significance.An overview of electrode parameters for some common electrode materials can be a valuable and useful tool in numerical bioelectronics models. A provided FEM implementation model can be readily adapted to arbitrary electrode geometries and used for various applications. Finally, the presented methodology for parametrization of electrode materials can be used for any materials of interest which were not covered by this work.

• Keywords
• bioelectronics, constant phase element, electrodes, interface, simulation,
• MeSH
• Finite Element Analysis MeSH
• Electric Impedance MeSH
• Electrodes * MeSH
• Dielectric Spectroscopy methods   MeSH
• Humans MeSH
• Computer Simulation MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

BACKGROUND: This study is focused on the opening technique of the cervical vertebrae during laminoplasty which serves to substantially reduce the most severe adverse effects of the simple resection of posterior vertebral elements. This computational study aims to clarify by an optimisation approach what shape and position upon the lamina the groove should have. METHODS: The computational model was developed in the computational software COMSOL Multiphysics 5.6a based on a computer tomography data obtained from the C4 vertebra. For finding the optimal minimum or maximum of a function (surface), optimisation algorithms are developed following the Nelder-Mead algorithm. RESULTS: The reaction-opening force increases with a decreasing groove radius and an increasing position from the vertebra body. The created area increases with a decreasing groove radius and a decreasing position. As the opening happens mostly only above the groove, the opening area increases only in this location. Moreover, the von Mises stress peak value is almost twice as large as in the case of maximization of the opening area, which might result in breaking of the lamina as the thickness of the lamina would be reduced to its minimum. CONCLUSION: The groove radius and position can affect the opening force and the opening area in case of double door laminoplasty. The opening force is highly influenced by the groove position and radius. The best position for placing the groove is in the middle of the lamina and the radius of the groove should be as large as possible.

• Keywords
• Laminoplasty, finite element method, groove position, optimisation, spine,
• MeSH
• Algorithms MeSH
• Biomechanical Phenomena MeSH
• Cervical Vertebrae diagnostic imaging   surgery   MeSH
• Laminoplasty * adverse effects   MeSH
• Humans MeSH
• Tomography, X-Ray Computed MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH

One of the remaining challenges in magnetic thermonuclear fusion is survival of the heat shield protecting the tokamak reactor vessel against excessive plasma heat fluxes. Unmitigated high confinement edge localized mode (ELM) is a regular heat pulse damaging the heat shield. We suggest a novel concept of magnetic sweeping of the plasma contact strike point fast and far enough in order to spread this heat pulse. We demonstrate feasibility of a dedicated copper coil in a resonant circuit, including the induced currents and power electronics. We predict the DEMO ELM properties, simulate heat conduction, 3D particles motion and magnetic fields of the plasma and coil in COMSOL Multiphysics and Matlab. The dominant system parameter is voltage, feasible 18 kV yields 1 kHz sweeping frequency, suppressing the ELM-induced surface temperature rise by a factor of 3. Multiplied by other known mitigation concepts, ELMs might be mitigated enough to ensure safe operation of DEMO.

• Publication type
• Journal Article MeSH

The finite element analysis technique was used to investigate the suitability of silver nanorods, spheres, ellipsoids and core−shell structures for the hyperthermia treatment of cancer. The temperature of the silver nanostructures was raised from 42 to 46 °C, in order to kill the cancerous cells. The time taken by the nanostructures to attain this temperature, with external source heating, was also estimated. The heat transfer module in COMSOL Multiphysics was used for the finite element analysis of hyperthermia, based on silver nanostructures. The thermal response of different shapes of silver nanostructures was evaluated by placing them inside the spherical domain of the tumor tissue. The proposed geometries were heated at different time intervals. Optimization of the geometries was performed to achieve the best treatment temperature. It was observed that silver nanorods quickly attain the desired temperature, as compared to other shapes. The silver nanorods achieved the highest temperature of 44.3 °C among all the analyzed geometries. Moreover, the central volume, used to identify the thermal response, was the maximum for the silver nano-ellipsoids. Thermal equilibrium in the treatment region was attained after 0.5 μs of heating, which made these structures suitable for hyperthermia treatment.

• Keywords
• COMSOL Multiphysics, finite element analyses, hyperthermia, silver nanostructures, surface coating,
• Publication type
• Journal Article MeSH

INTRODUCTION: Conventional biopsy, based on extraction from a tumor of a solid tissue specimen requiring needles, endoscopic devices, excision or surgery, is at risk of infection, internal bleeding or prolonged recovery. A non-invasive liquid biopsy is one of the greatest axiomatic consequences of the identification of circulating tumor DNA (ctDNA) as a replaceable surgical tumor bioQpsy technique. Most of the literature studies thus far presented ctDNA detection at almost final stage III or IV of cancer, where the treatment option or cancer management is nearly impossible for diagnosis. OBJECTIVE: Hence, this paper aims to present a simulation study of extraction and separation of ctDNA from the blood plasma of cancer patients of stage I and II by superparamagnetic (SPM) bead particles in a microfluidic platform for early and effective cancer detection. METHOD: The extraction of ctDNA is based on microfiltration of particle size to filter some impurities and thrombocytes plasma, while the separation of ctDNA is based on magnetic manipulation to high yield that can be used for the upstream process. RESULT: Based on the simulation results, an average of 5.7 ng of ctDNA was separated efficiently for every 10 µL blood plasma input and this can be used for early analysis of cancer management. The particle tracing module from COMSOL Multiphysics traced ctDNA with 65.57% of sensitivity and 95.38% of specificity. CONCLUSION: The findings demonstrate the ease of use and versatility of a microfluidics platform and SPM bead particles in clinical research related to the preparation of biological samples. As a sample preparation stage for early analysis and cancer diagnosis, the extraction and separation of ctDNA is most important, so precision medicine can be administered.

• Keywords
• COMSOL Multiphysics Simulation study, Cancer biomarker, Circulating tumor DNA (ctDNA) detection, Liquid biopsy Magnetic manipulation,
• MeSH
• Circulating Tumor DNA * MeSH
• Humans MeSH
• Magnetic Iron Oxide Nanoparticles MeSH
• Microfluidics MeSH
• Neoplasms * diagnosis   MeSH
• Liquid Biopsy MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Circulating Tumor DNA * MeSH

INTRODUCTION AND HYPOTHESIS: Quantitative characterization of the birth canal and critical structures before delivery may provide risk assessment for maternal birth injury. The objective of this study was to explore imaging capability of an antepartum tactile imaging (ATI) probe. METHODS: Twenty randomly selected women older than 21 years with completed 35th week of pregnancy and a premise of vaginal delivery were enrolled in the feasibility study. The biomechanical data were acquired using the ATI probe with a double-curved surface, shaped according to the fetal skull and equipped with 168 tactile sensors and an electromagnetic motion tracking sensor. Software package COMSOL Multiphysics was used for finite element modeling. Subjects were asked for assessment of pain and comfort levels experienced during the ATI examination. RESULTS: All 20 nulliparous women were successfully examined with the ATI. Mean age was 27.8 ± 4.1 years, BMI 30.7 ± 5.8, and week of pregnancy 38.8 ± 1.4. Biomechanical mapping with the ATI allowed real-time observation of the probe location, applied load to the vaginal walls, and a 3D tactile image composition. The nonlinear finite element model describing the stress-strain relationship of the pelvic tissue was developed and used for calculation of Young's modulus (E). Average perineal elastic modulus was 11.1 ± 4.3 kPa, levator ani 4.8 ± 2.4 kPa, and symphysis-perineum distance was 30.1 ± 6.9 mm. The pain assessment level for the ATI examination was 2.1 ± 0.8 (scale 1-4); the comfort level was 2.05 ± 0.69 (scale 1-3). CONCLUSIONS: The antepartum examination with the ATI probe allowed measurement of the tissue elasticity and anatomical distances. The pain level was low and the comfort level was comparable with manual palpation.

• Keywords
• Biomechanics of parturition, Elastography, Finite element model, Perineal elasticity, Tactile imaging,
• MeSH
• Adult MeSH
• Elasticity Imaging Techniques * MeSH
• Humans MeSH
• Young Adult MeSH
• Pelvic Floor * diagnostic imaging   MeSH
• Perineum diagnostic imaging   MeSH
• Parturition MeSH
• Feasibility Studies MeSH
• Pregnancy MeSH
• Imaging, Three-Dimensional MeSH
• Check Tag
• Adult MeSH
• Humans MeSH
• Young Adult MeSH
• Pregnancy MeSH
• Female MeSH
• Publication type
• Journal Article MeSH

A transformation-optical method is presented to enhance the directivity of a cylindrical wire antenna by using an all-dielectric graded index medium. The strictly conformal mapping between two doubly connected virtual and physical domains is established numerically. Multiple directive beams are produced, providing directive emission. The state-of-the-art optical path rescaling method is employed to mitigate the superluminal regions. The resulting transformation medium is all-dielectric and nondispersive, which can provide broadband functionality and facilitate the realization of the device using available fabrication technologies. The realization of the device is demonstrated by dielectric perforation based on the effective medium theory. The device's functionality is verified by carrying out both ray-tracing and full-wave simulations using finite-element-based software COMSOL Multiphysics.

• Publication type
• Journal Article MeSH

In the Czech part of the Upper Silesian Coal Basin (Moravian-Silesian region, Czech Republic), there are many deposits of endogenous combustion (e.g., localized burning soil bodies, landfills containing industrial waste, or slag rocks caused by mining processes). The Hedwig mining dump represents such an example of these sites where, besides the temperature and the concentrations of toxic gases, electric and non-electric quantities are also monitored within the frame of experimentally proposed and patented technology for heat collection (the so-called "Pershing" system). Based on these quantities, this paper deals with the determination and evaluation of negative heat sources and the optimization of the positive heat source dependent on measured temperatures within evaluation points or on a thermal profile. The optimization problem is defined based on a balance of the heat sources in the steady state while searching for a local minimum of the objective function for the heat source. From an implementation point of view, it is the interconnection of the numerical model of the heat collector in COMSOL with a user optimization algorithm in MATLAB using the LiveLink for MATLAB. The results are elaborated in five case studies based on the susceptibility testing of the numerical model by input data from the evaluation points. The tests were focused on the model behavior in terms of preprocessing for measurement data from each chamber of the heat collector and for the estimated value of temperature differences at 90% and 110% of the nominal value. It turned out that the numerical model is more sensitive to the estimates in comparison with the measured data of the chambers, and this finding does not depend on the type optimization algorithm. The validation of the model by the use of the mean-square error led to the finding of optimal value, also valid with respect to the other evaluation.

• Keywords
• COMSOL multiphysics, MATLAB, borehole heat exchanger (BHE), liveLink for MATLAB, optimization, partial differential equation,
• Publication type
• Journal Article MeSH