Browsing by Subject "Finite element method (FEM)"

Now showing 1 - 4 of 4

Open Access
In-plane-sensing analysis of comb-like capacitive micro-machined ultrasonic transducers (cmuts) using analytical small-signal model and fem
(Institute of Electrical and Electronics Engineers, 2023-04-18) Zhang, S.; Lu, W.; Yang, Y.; Wang, R.; Zhang, G.; Xu, B.; Yılmaz, Metin; Zhang, W.
In this work, capacitive micro-machined ultrasonic transducers (CMUTs) were developed into comb-like shapes to make these comb-like shaped structures work for sensing in-plane vibrations of ultrasonic guided waves. On this basis, an analytical small-signal model, which is mainly a combination of the forced vibration theory and the simplified parallel-plate capacitor model, was proposed to satisfy the requirements of theoretical design. Through the proposed model, the in-plane-sensing behaviors of a comb-like CMUT cell can be predicted, including vibrating velocity, output current, and sensitivity. Compared with the results calculated from the finite element method (FEM) simulation, it was found that the static state and the frequency-domain results of the analytical small-signal model agree well with those of FEM simulations if the used first natural frequencies of these two methods are identical. Considering the fringing field capacitance could further improve the accuracy of the analytical small-signal model. At last, influences of some external parameters, i.e., dc bias voltage, air damping, and input in-plane displacement, on the sensitivity of a comb-like CMUT cell were discussed by the analytical small-signal model and FEM simulation. Relevant results reveal the way to design a comb-like CMUT and indicate the conditions when the analytical small-signal model is accurate. Our work develops the theory on the in-plane-sensing comb-like CMUT and is expected to be combined with the theory on the previous out-of-plane-sensing CMUT to realize 3-D-CMUT for sensing 3-D guided waves.
Open Access
Modeling of thermal sensitivity of a fiber optic gyroscope coil with practical quadrupole winding
(SPIE, 2017) Ogut, Serdar; Osunluk B.; Özbay, Ekmel
Thermally induced bias error is one of the main performance limits for the fiber optic gyroscopes (FOGs). We reviewed the thermal sensitivity of FOG in detail and created a simulation environment by the Finite Element Method (FEM). Thermal sensitivity analysis is based on Shupe and elastooptic effects. Elastooptical interactions are modeled by using the two different FEM simulations and homogenization-dehomogenization processes. FEM simulations are validated by comparing the results with a laboratory FOG setup. We report the changes in the error characteristics for practical quadruple winding patterns. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
Open Access
RF heating of deep brain stimulation implants in open-bore vertical MRI systems: a simulation study with realistic device configurations
(International Society for Magnetic Resonance in Medicine, 2020) Golestanirad, L.; Kazemivalipour, Ehsan; Lampman, D.; Habara, H.; Atalar, Ergin; Rosenow, J.; Pilitsis, J.; Kirsch, J.
Purpose Patients with deep brain stimulation (DBS) implants benefit highly from MRI, however, access to MRI is restricted for these patients because of safety hazards associated with RF heating of the implant. To date, all MRI studies on RF heating of medical implants have been performed in horizontal closed‐bore systems. Vertical MRI scanners have a fundamentally different distribution of electric and magnetic fields and are now available at 1.2T, capable of high‐resolution structural and functional MRI. This work presents the first simulation study of RF heating of DBS implants in high‐field vertical scanners. Methods We performed finite element electromagnetic simulations to calculate specific absorption rate (SAR) at tips of DBS leads during MRI in a commercially available 1.2T vertical coil compared to a 1.5T horizontal scanner. Both isolated leads and fully implanted systems were included. Results We found 10‐ to 30‐fold reduction in SAR implication at tips of isolated DBS leads, and up to 19‐fold SAR reduction at tips of leads in fully implanted systems in vertical coils compared to horizontal birdcage coils. Conclusions If confirmed in larger patient cohorts and verified experimentally, this result can open the door to plethora of structural and functional MRI applications to guide, interpret, and advance DBS therapy.
Open Access
Simulation-based engineering
(Springer, 2017) Çakmakcı, Melih; Sendur, G. K.; Durak, U.; Mittal, S.; Durak, U.; Ören, T.
Engineers, mathematicians, and scientists were always interested in numerical solutions of real-world problems. The ultimate objective within nearly all engineering projects is to reach a functional design without violating any of the performance, cost, time, and safety constraints while optimizing the design with respect to one of these metrics. A good mathematical model is at the heart of each powerful engineering simulation being a key component in the design process. In this chapter, we review role of simulation in the engineering process, the historical developments of different approaches, in particular simulation of machinery and continuum problems which refers basically to the numerical solution of a set of differential equations with different initial/boundary conditions. Then, an overview of well-known methods to conduct continuum based simulations within solid mechanics, fluid mechanics and electromagnetic is given. These methods include FEM, FDM, FVM, BEM, and meshless methods. Also, a summary of multi-scale and multi-physics-based approaches are given with various examples. With constantly increasing demands of the modern age challenging the engineering development process, the future of simulations in the field hold great promise possibly with the inclusion of topics from other emerging fields. As technology matures and the quest for multi-functional systems with much higher performance increases, the complexity of problems that demand numerical methods also increases. As a result, large-scale effective computing continues to evolve allowing for efficient and practical performance evaluation and novel designs, hence the enhancement of our thorough understanding of the physics within highly complex systems.