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The purpose of this study is to determine the contamination level in natural water resources because the tremendous development in the agriculture sector has increased the amount of contamination in natural water sources. Hence, the water is polluted and unsafe to drink.

Three types of sensor arrays were suggested: parallel, star and delta. The simulation of all types of sensor array was carried out to calculate the sensors’ impedance value, capacitance and inductance during their operation to determine the best sensor array. The contamination state was simulated by altering the electrical properties values of the environmental domain of the model to represent water contamination.

The simulation results show that all types of sensor array are sensitive to conductivity, σ, and permittivity, ɛ (i.e. contaminated water). Furthermore, a set of experiments was conducted to determine the relationship between the sensor’s impedance and the water’s nitrate and sulphate contamination. The performance of the system was observed where the sensors were tested, with the addition of distilled water with different concentrations of potassium nitrate and potassium sulphate. The sensitivity of the developed sensors was evaluated and the best sensor was selected.

Based on the outcomes of the experiments, the star sensor array has the highest sensitivity and can be used to measure nitrate and sulphate contaminations in water.

The star sensor array presented in this paper has the potential to be used as a useful low-cost tool for water source monitoring.

The substrate coupling and loss in integrated circuits are analyzed. Then, the authors extract impedances between any numbers of embedded contacts. The paper aims to discuss these issues.

The paper proposes a new substrate network 3D extraction technique, adapted from a transmission line method or Green kernels, but in the whole volume.

Extracting impedances between any numbers of embedded contacts with variable shapes or/and through silicon via. This 3D method is much faster comparing with FEM

Previous works consider TSVs alone, contacts onto the substrate. The authors do study entanglement between the substrate and the interconnections.

Recent work has demonstrated the possibility of selectively sintering polymer powders with radio frequency (RF) radiation as a means of rapid, volumetric additive manufacturing. Although RF radiation can be used as a volumetric energy source, non-uniform heating resulting from the sample geometry and electrode configuration can lead to adverse effects in RF-treated samples. This paper aims to address these heating uniformity issues by implementing a computational design strategy for doped polymer powder beds to improve the RF heating uniformity.

Two approaches for improving the RF heating uniformity are presented with the goal of developing an RF-assisted additive manufacturing process. Both techniques use COMSOL Multiphysics® to predict the temperature rise during simulated RF exposure for different geometries. The effectiveness of each approach is evaluated by calculating the uniformity index, which provides an objective metric for comparing the heating uniformity between simulations. The first method implements an iterative heuristic tuning strategy to functionally grade the electrical conductivity within the sample. The second method involves reorienting the electrodes during the heating stage such that the electric field is applied in two directions.

Both approaches are shown to improve the heating uniformity and predicted part geometry for several test cases when applied independently. However, the greatest improvement in heating uniformity is demonstrated by combining the approaches and using multiple electrode orientations while functionally grading the samples.

This work presents an innovative approach for overcoming RF heating uniformity issues to improve the resulting part geometry in an RF-assisted, volumetric additive manufacturing method.

During thermal laser processes, heat transfer and fluid flow in the melt pool are primary driven by complex physical phenomena that take place at liquid/vapor interface. Hence, the choice and setting of front description methods must be done carefully. Therefore, the purpose of this paper is to investigate to what extent front description methods may bias physical representativeness of numerical models of laser powder bed fusion (LPBF) process at melt pool scale.

Two multiphysical LPBF models are confronted: a Level-Set (LS) front capturing model based on a C++ code and a front tracking model, developed with COMSOL Multiphysics® and based on Arbitrary Lagrangian–Eulerian (ALE) method. To do so, two minimal test cases of increasing complexity are defined. They are simplified to the largest degree, but they integrate multiphysics phenomena that are still relevant to LPBF process.

LS and ALE methods provide very similar descriptions of thermo-hydrodynamic phenomena that occur during LPBF, providing LS interface thickness is correctly calibrated and laser heat source is implemented with a modified continuum surface force formulation. With these calibrations, thermal predictions are identical. However, the velocity field in the LS model is systematically underestimated compared to the ALE approach, but the consequences on the predicted melt pool dimensions are minor.

This study fulfils the need for comprehensive methodology bases for modeling and calibrating multiphysical models of LPBF at melt pool scale. This paper also provides with reference data that may be used by any researcher willing to verify their own numerical method.

The paper introduces and illustrates the use of numerical models for the simulation of electromagnetic and thermal processes in an absorbing ceramic layer (susceptor) of a new millimeter-wave (MMW) heat exchanger. The purpose of this study is to better understand interaction between the MMW field and the susceptor, choose the composition of the ceramic material and help design the physical prototype of the device.

A simplified version of the heat exchanger comprises a rectangular block of an aluminum nitride (AlN) doped with molybdenum (Mo) that is backed by a thin metal plate and irradiated by a plane MMW. The coupled electromagnetic-thermal problem is solved by the finite-difference time-domain (FDTD) technique implemented in QuickWave. The FDTD model is verified by solving the related electromagnetic problem by the finite element simulator COMSOL Multiphysics. The computation of dissipated power and temperature is based on experimental data on temperature-dependent dielectric constant, loss factor, specific heat and thermal conductivity of the AlN:Mo composite. The non-uniformity of patterns of dissipated power and temperature is quantified via standard-deviation-based metrics.

It is shown that with the power density of the plane wave on the block’s front face of 1.0 W/mm², at 95 GHz, 10 × 10 × 10-mm blocks with Mo = 0.25 – 4% can be heated up to 1,000 °C for 60-100 s depending on Mo content. The uniformity of the temperature field is exceptionally high – in the course of the heating, temperature is evenly distributed through the entire volume and, in particular, on the back surface of the block. The composite producing the highest level of total dissipated power is found to have Mo concentration of approximately 3%.

In the electromagnetic model, the heating of the AlN:Mo samples is characterized by the volumetric patterns of density of dissipated power for the dielectric constant and the loss factor corresponding to different temperatures of the process. The coupled model is run as an iterative procedure in which electromagnetic and thermal material parameters are upgraded in every cell after each heating time step; the process is then represented by a series of thermal patterns showing time evolution of the temperature field.

Determination of practical dimensions of the MMW heat exchanger and identification of material composition of the susceptor that make operations of the device energy efficient in the required temperature regime require and expensive experimentation. Measurement of heat distribution on the ceramic-metal interface is a practically challenging task. The reported model is meant to be a tool assisting in development of the concept and supporting system design of the new MMW heat exchanger.

While exploitation of a finite element model (e.g. in COMSOL Multiphysics environment) of the scenario in question would require excessive computational resources, the reported FDTD model shows operational capabilities of solving the coupled problem in the temperature range from 20°C to 1,000°C within a few hours on a Windows 10 workstation. The model is open for further development to serve in the ongoing support of the system design aiming to ease the related experimental studies.

The purpose of this paper is to investigate the reliability of wire bonds with three varying ball bond diameters, which are ball bonded with three different sizes of gold wires in light-emitting diode (LED) package under high-temperature environment. In automotive applications, “lifted ball bond” issue is a potential critical point for LED device reliability, as the wire bonds are usually stressed under high operating temperature during their lifetime. Moreover, the reliability of wire bonds in recent LED production has fallen under scrutiny due to the practice of reducing wire diameters to cut down production costs.

Three gold wires with sizes of 2, 1.5 and 1 mm were ball bonded on the LED chip bond pad via thermosonic wire bonding method to produce three different ball bond diameters, that is, 140, 120 and 100 μm, respectively. The reliability of these wire bond samples was then studied by performing isothermal aging at 200°C for the time interval of 30, 100 and 500 hours. To validate hypotheses based on the experimental data, COMSOL Multiphysics simulation was also applied to study the thermal stress distribution of wire bond under an elevated temperature.

Experimental results show that the interfacial adhesion of wire bond degrades significantly after aging at 200°C for 500 hours, and the rate of interfacial degradation was found to be more rapid in the wire bond with smaller ball bond diameter. Experimental results also show that ball bonds randomly elongate along an axis and deforms into elliptical shapes after isothermal aging, and ball bonds with smaller diameters develop more obvious elongations. This observation has not been reported in any previous studies. Simulation results show that higher thermal stress is induced in the wire bond with the decrease of ball bond diameter.

The reliability study of this paper provides measurements and explanation on the effects of wire diameter downsizing in wire bonds for automotive application. This is applicable as a reliability reference for industries who intend to reduce their production costs. Other than that, the analysis method of thermal stresses using COMSOL Multiphysics simulations can be extended by other COMSOL Multiphysics users in the future.

To resolve “lifted ball bond” issue, optimization of the bond pad surface quality and the wire bond parameter has been studied and reported in many studies, but the influence of ball bond diameter on wire bond reliability is rarely focused. Moreover, the observation of ball bonds randomly elongate and deform more into elliptical shape, and ball bond with smaller diameter has the highest elongation after isothermal aging also still has not been reported in any previous studies.

The purpose of this paper is to present a model that can be used to simulate the photopolymerization process in micro‐stereolithography (SL) in order to predict the shape of the cured parts. SL is an additive manufacturing process in which liquid photopolymer resin is cross‐linked and converted to solid with a UV laser light source. Traditional models of SL processes do not consider the complex chemical reactions and species transport occurring during photopolymerization and, hence, are incapable of accurately predicting resin curing behavior. The model presented in this paper attempts to bridge this knowledge gap.

The chemical reactions involved in the photopolymerization of acrylate‐based monomers were modeled as ordinary differential equations (ODE). This model incorporated the effect of oxygen inhibition and diffusion on the polymerization reaction. The model was simulated in COMSOL and verified with experiments conducted on a mask‐based micro‐SL system. Parametric studies were conducted to investigate the possibilities to improve the accuracy of the model for predicting the edge curvature.

The proposed model predicts well the effect of oxygen inhibition and diffusion on photopolymerization, and the model accurately predicts the cured part height when compared to experiments conducted on a mask‐based SL system. The simulated results also show the characteristic edge curvature as seen in experiments.

A triacrylate monomer was used in the experiments conducted, so results may be limited to acrylate monomers. Shrinkage was not considered when comparing cured part shapes to those predicted using COMSOL.

This paper presents a unique and a pioneering approach towards modeling of the photopolymerization reaction in micro‐SL process. This research furthers the development of patent pending film micro‐SL process which can be used for fabrication of custom micro‐optical components.

Detection of low-frequency pressures such as heart rate in the range of 1 Hz is one of the applications of low-frequency resonator. In this paper, the structure of the resonator is in the form of a plate, whose mathematical model has been extracted according to past works and is reported.

This paper presents an electromechanical microresonator that can be used as an ultra-low-frequency pressure sensor. It is very important to choose the right material for the sensors to have the optimal conditions. In this work, by proposing the innovative use of polytetrafluoroethylene material with low stiffness coefficient, the necessary conditions are provided to reduce the vibration frequency of the resonator.

The proposed design is simulated with the help of COMSOL, and its results are compared with the results of the mathematical model, which are very close to each other. Therefore, by inferring the results, the authors can rely on accurate simulations and finalize the similar designs with full confidence before fabrication.

There are important advantages regarding the geometry of the proposed design structure that is the possibility of detecting a pressure of 1 Pa only with voltages less than 2 V. On the other hand, the pull-in effect causes very low frequencies to be achieved in detection with the help of the proposed resonator. Also, the linear and nonlinear behavior of the resonator by applying different pressures has been studied and reported to find the appropriate operating range of the resonator and its limitations.

The purpose of this paper is to study an electrolytic etching method to prepare fine lines on printed circuit board (PCB). And the influence of organics on the side corrosion protection of PCB fine lines during electrolytic etching is studied in detail.

In this paper, the etching factor of PCB fine lines produced by new method and the traditional method was analyzed by the metallographic microscope. In addition, field emission scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to study the inhibition of undercut of the four organometallic corrosion inhibitors with 2,5-dimercapto-1,3,4-thiadiazole, benzotriazole, l-phenylalanine and l-tryptophan in the electrolytic etching process.

The SEM results show that corrosion inhibitors can greatly inhibit undercut of PCB fine lines during electrolytic etching process. XPS results indicate that N and S atoms on corrosion inhibitors can form covalent bonds with copper during electrolytic etching process, which can be adsorbed on sidewall of PCB fine lines to form a dense protective film, thereby inhibiting undercut of PCB fine lines. Quantum chemical calculations show that four corrosion inhibitor molecules tend to be parallel to copper surface and adsorb on copper surface in an optimal form. COMSOL Multiphysics simulation revealed that there is a significant difference in the amount of corrosion inhibitor adsorbed on sidewall of the fine line and the etching area.

As a clean production technology, electrolytic etching method has a good development indicator for the production of high-quality fine lines in PCB industry in the future. And it is of great significance in saving resources and reducing environmental pollution.

The purpose of this paper is to present the development and application of a numerical formulation for the structural dynamics and aeroelastic analysis of new generation helicopter and tiltrotor rotor blades. These are characterized by a curvilinear elastic axis, typically with the presence of tip sweep and anhedral angles.

The structural dynamics model implemented is based on nonlinear, flap‐lag‐torsion, rotating beam equations that are valid for slender, homogeneous, isotropic, non‐uniform, twisted blades undergoing moderate displacements. A second‐order approximation scheme for strain‐displacement is adopted. Aerodynamic contributions for aeroelastic applications are derived from sectional theories, with inclusion of wake inflow models to take into account three‐dimensional effects. The numerical integration is obtained through implementation within the COMSOL Multiphysics Finite‐Element‐Method (FEM) software code, considering the elastic axis of arbitrary curvilinear shape.

The computational tool developed is validated by comparisons with results available in the literature. These demonstrate the capability of the tool to accurately predict structural dynamics and aeroelastic behavior of curved‐axis rotor blades. In particular, the influence of sweep and anhedral angles at the blade tip is successfully captured.

The numerical tool developed is limited to the analysis of isotropic blades, with a simple sectional aerodynamic modeling for aeroelastic applications. However, the flexibility of the process through which the proposed tool has been developed is such that a moderate effort is required for its extension to composite blades and more accurate aerodynamic loads predictions.

The proposed computational solver is a reliable tool for preliminary design and optimal design processes of helicopter and tiltrotor rotor blades.

Computational tools for rotors with advanced‐geometry blades are not commonly available. Therefore, the presentation of a successful way to implement structural dynamics/aeroelastic mathematical formulations for rotor blades with curvilinear elastic axis in highly flexible, multiphysics, FEM‐based, commercial software may be of interest for designers and researchers.