Authors:Cahyo Aji Hapsoro, Wahyu Srigutomo, Acep Purqon, Warsa warsa, Doddy Sutarno, Tsuneomi Kagiyama Abstract: Global optimization inversion of grounded wire time-domain electromagnetic (TDEM) data was implemented through application of the particle swarm optimization (PSO) algorithm. This probabilistic approach is an alternative to the widely used deterministic local-optimization approach. In the PSO algorithm, each particle that constitutes the swarm epitomizes a probable geophysical model comprised by subsurface resistivity values at several layers and layer thicknesses. The forward formulation of the TDEM problem for calculating the vertical component of the induced magnetic field is first expressed in the Laplace domain. Transformation of the magnetic field from the Laplace domain into the time domain is performed by applying the Gaver-Stehfest numerical method. The implementation of PSO inversion to the TDEM problem is straightforward. It only requires adjustment of a few inversion parameters such as inertia, acceleration coefficients and numbers of iteration and particles. The PSO inversion scheme was tested on synthetic noise-free data and noisy synthetic data as well as to field data recorded in a volcanic-geothermal area. The results suggest that the PSO inversion scheme can effectively solve the TDEM 1D stratified earth problem. PubDate: 2021-01-18 Issue No:Vol. 53 (2021)
Authors:Ridho Hantoro, Sarwono Sarwono, Fernando Parsaulian Panjaitan, Erna Septyaningrum, Nuril Hidayati Abstract: The Vertical Axis Hydrokinetic Turbine – Straight Blade Cascaded (VAHT-SBC) is a type of energy generation technology developed to meet the increasing demand for renewable energy. Previous studies have been carried out to enhance the efficiency of the turbine through several aspects. To deploy a turbine on site, a study on its power generation and conversion is needed. In this research, the VAHT–SBC was integrated with a permanent magnet synchronous generator (PMSG) by a pulley and belt transmission system. This study was conducted by experimental and numerical analysis. The CFD simulation result showed that the highest torque of the turbine was found at 0° and 360°, with an average value of 23.923 Nm and with current velocity at 0.92 m/s. The experimental data showed that the voltage and frequency were proportional to the generator rotational speed and inversely correlated with the load given to the integration system. In the inverter, the voltage and frequency values were stable at 230 V and 56 Hz respectively. The VAHT-SBC prototype was able to produce a maximum power of 50 W on site, with a current velocity of 0.82 and 0.92 m/s. PubDate: 2021-01-18 Issue No:Vol. 53 (2021)
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