Abstract. Vertical electrical sounding (VES) data are usually interpreted in terms of a 1D resistivity model using linearized inversion. The local approach of a non-linear inverse problem has fundamental limitations, i.e. the necessity of a starting model close to the solution and possible convergence to a local rather than a global minimum solution. We studied the application of a global search approach for non-linear inversion using the guided random search method to model VES data. A quasi-2D resistivity model can be created by stitching 1D models obtained from VES data along a profile. Both vertical and lateral resistivity variations are minimized to incorporate a 2D smoothness constraint. The proposed method was applied to invert synthetic VES data as well as field data from a sedimentary environment. Both synthetic and field data inversions resulted in models that correlated well with the known synthetic model and with the geology of the study area, respectively.

The 3D distribution of hydraulic conductivity in the unconfined aquifer is needed to understand the interaction between groundwater and Citarum River, which may relate to water contamination and flooding. In this study, it was estimated using the geostatistical method. The data used are the hydraulic conductivity parameter from thirteen large-diameter dug wells determined using the slug test method. Further analysis was conducted using groundwater and Citarum River physical parameters, i.e. total dissolved solids, pH, and temperature. The results show that the hydraulic conductivity of the unconfined aquifer in the Upper Citarum River ranges from 8.34 x 10−7 to 2.19 x 10−5 m/s. The area with relatively high hydraulic conductivity, i.e. Ciparay and Solokan Jeruk Sub-districts, will have a greater possibility of groundwater or river water contamination depending on their interaction. Meanwhile, the area with relatively flat topography and low hydraulic conductivity, i.e. Majalaya and Baleendah Sub-districts, will be more susceptible to flood. Therefore, the mitigation of water contamination and flooding in the Upper Citarum River should consider the 3D hydraulic conductivity distribution, e.g. by monitoring the groundwater quality in some dug wells located in high hydraulic conductivity area and installing recharge or injection well to eliminate the artificial runoff.

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This study aims to examine the achievement and improvement of the ability of understanding and mathematical reasoning and motivation through Think Talk Write (TTW) approach to junior high school students. The population in this study is all junior high school in West Bandung Regency and the sample is class VIII of SMPS Darun Nasya, The instrument used in the research is a question of understanding and mathematical reasoning and questionnaire of learning motivation attitude, then the data obtained is processed through a two-way ANOVA test and correlation and regression test, data processing using IBM Statistics SPSS 21. Results of research involving TTW as independent variables in the experimental class and direct learning in the control class showed: There was a difference in achievement and improvement of mathematical understanding between control and experiment class, There are differences in achievement and improvement of mathematical reasoning between control and experiment class, There is difference of student's learning motivation between control and experiment class.

This paper was presented in The 3rd Padjadjaran International Physics Symposium 2017, Holiday-Inn Hotel, Bandung , 14-15 November 2017, Department of Physics Universitas Padjadjaran. Authors: Prihadi Sumintadireja1, Ihsan Imaduddin2,4, Wahyu Srigutomo2, Enjang Jaenal Mustopa2, Diky Irawan3, Ihsanuddin A. Lubis3. Abstract: This paper demonstrated a new geolectrical equipment of LVG GLS multi channel , which as part of Laboratory of Application and Geosciences Modeling research, which funded by Institut Teknologi Bandung. Initially, the LVG GLS equipment is designed for delineating geothermal area by mise a la masse configuration. Furthermore, the application is plan to modify for geohazard study, since many landslide occurrence without clear explanation about the involving process due to lack data measurement. The ability of equipment is able to measure resistivity of subsurface condition in real time and continuous. Therefore, spatial and temporal data for monitoring vulnerable landslide area, which identified by geological mapping can be visualized to mitigate the geohazard area more precisely. The simultaneous 80 channel electrode measurement can reduced inhomogeneity of spontaneous potential value, which change by time interval.