Comprehensive Optimization of the Tripolar Concentric Ring Electrode Based on Its Finite Dimensions Model and Confirmed by Finite Element Method Modeling

The optimization performed in this study is based on the finite dimensions model of the concentric ring electrode as opposed to the negligible dimensions model used in the past. This makes the optimization problem comprehensive, as all of the electrode parameters including, for the first time, the radius of the central disc and individual widths of concentric rings, are optimized simultaneously. The optimization criterion used is maximizing the accuracy of the surface Laplacian estimation, as the ability to estimate the Laplacian at each electrode constitutes primary biomedical significance of concentric ring electrodes. For tripolar concentric ring electrodes, the optimal configuration was compared to previously proposed linearly increasing inter-ring distances and constant inter-ring distances configurations of the same size and based on the same finite dimensions model. The obtained analytic results suggest that previously proposed configurations correspond to almost two-fold and more than three-fold increases in the Laplacian estimation error compared with the optimal configuration proposed in this study, respectively. These analytic results are confirmed using finite element method modeling, which was adapted to the finite dimensions model of the concentric ring electrode for the first time. Moreover, the finite element method modeling results suggest that optimal electrode configuration may also offer improved sensitivity and spatial resolution.

Analisis Tegangan pada Terowongan Bawah Tanah Dengan Metode Elemen Hingga

Construction of tunneling in Indonesia is a new thing to be implemented, especially in the capital city of Jakarta, which has land issues for surface transportation. In the construction stage of tunnels, the problem of deformation and stress to the surface of the excavation needs to be considered carefully. Therefore, the purpose of this paper is to analyze the stresses and deformations that occur in underground tunnels during the construction stage using the finite element method. Modeling is done in full 3 dimensions using a finite element based MIDAS GTS NX program. The results of the study showed that the increase in construction stage, the value of deformation that occurs in development will increase. It also occurs in stress, the more construction phases increase the greater the stress value. Shield release has an effect on increasing the stress, causing the stress to increase even greater. This study uses a hybrid mesher element to model the soil and tunnel layers. From this modeling is expected to be the beginning of complex and good tunnel modeling in the future.Keywords: Tunnel, MIDAS GTS NX, stress, Deformation, construction stage, finite element method.