JURNAL ILMU FISIKA | UNIVERSITAS ANDALAS

Characterization of Silicon from Rice Husk Doped with Cobalt: Analysis of Structure and Magnetoelectric Properties

Rizky Kurniawan, Andriayani Andriayani, Saharman Gea, Hadi Kurniawan — Thu, 25 Apr 2024 00:00:00 +0700

The development of Si-based materials has attracted increasing attention, particularly for application in semiconductors, batteries, sensors, and optical technology. Silicon has abundant availability, high energy storage capacity, and low work potential. However, it faces compatibility challenges due to its low electrical conductivity and extremely small magnetic susceptibility. This research aimed to investigate the influence of Co dopants on the structure, morphology, electrical conductivity, and magnetic susceptibility of silicon. Silicon was synthesized using the magnesiothermic reduction method, and silicon was modified with Co metal dopants at 0.1% and 0.5% concentrations through the impregnation method. XRD analysis results showed that Si, 0.1% Co/Si, and 0.5% Co/Si exhibit silicon diffraction patterns at 2θ = 28.42º; 47.28º; 56.11º; 69.13º; and 76.36º. The morphology of Si and Co/Si revealed a rough, uneven, and porous surface with particles appearing spherical. Electrical conductivity increases with Co concentration: Si = 1223 µS/cm, 0.1% Co/Si= 1376 µS/cm, and 0.5% Co/Si= 1529 µS/cm. Magnetic susceptibility measurements indicated that Si, 0.1% Co/Si, and 0.5% Co/Si are paramagnetic at a range of 1.18 x10^-6 to 1.25 x10^-5 SI. These characterization results confirmed that the modification with Co dopants can enhance the magnetoelectric properties of silicon.

Validation of OpenMC Code for Low-cycle and Low-particle Simulations in the Neutronic Calculation

Sun, 19 May 2024 00:00:00 +0700

Validation of Low-Cycle and Low-Particle OpenMC Simulation Codes for Neutronics Calculations has been conducted. This study validates OpenMC, an evolving open-source neutron analysis code. Validation of Low-Cycle and Low-Particle Codes is crucial as it allows for effective calculations with minimal computational resources. Determining the convergence point of cycles and minimum particles in low-cycle and low-particle calculations enables maintaining calculation accuracy, thus providing sufficiently accurate results. This study demonstrates that a minimum of 15,000 particles, 100 cycles (30 inactive, 70 active), is required for low-cycle simulations. A comparison of k-eff calculation results with the SRAC code for MSR FUJI-12 at 7 burnup points (0-27 MWd/ton) yields a maximum error of 0.7%. These results validate the effectiveness of OpenMC in achieving accurate neutronic calculations with limited computational resources

Integration of a Smart Power Meter for Monitoring Household Energy Consumption in Prepaid Electrical Systems

Indah Permatasari, Danny Kurnianto — Wed, 10 Jul 2024 00:00:00 +0700

Indonesian households have widely embraced the prepaid electricity payment system. The system relies on electricity credits, with each electrical device consuming credits as a unit of measurement for energy usage. A common issue is the automatic cutoff of electricity supply when the credits are depleted. This research designed a smart power meter using Current Transformer and voltage sensors. The electrical token value is then stored in the Arduino's EEPROM before being transmitted to the NodeMCU. The NodeMCU transfers the data to Antares using the MQTT protocol to forward it to the subscriber, typically an Android device. The data sent to the Android application includes current, voltage, active power, frequency, cos φ, and electrical credits. The measurement of electricity consumption on a kWh meter involves subtracting the value of the input electricity token from the device-measured electricity usage. The device sends a WhatsApp message when the remaining credit exceeds 10 kWh. The prototype of the smart power meter demonstrates practical functionality, with the current sensor accuracy at 99.983% and the voltage sensor accuracy at 99.999%. The largest measurement difference of the electric credit balance between the PLN Meter and the prototype is 0.04 kWh over a test period of 72 hours.

Trends in Water Vapor and Ozone Concentrations at Several Altitudes in the Indonesian Region due to the La Niña Phenomenon

Silvi Ariani, Mutya Vonnisa, Marzuki Marzuki — Sun, 28 Jul 2024 00:00:00 +0700

We observed the effect of the La Niña phenomenon on the concentration of water vapor and ozone in the Indonesian region. This aims to the value of water vapor and ozone concentrations due to the La Niña phenomenon using Microwave Limb Sounder (MLS) data from 2004-2022. The La Niña phenomenon was chosen because during La Niña, the sea surface temperature in Indonesia is warmer than normal, thus increasing the evaporation of sea water which result is an increase in the concentration of water vapor in the atmosphere. Concentration values are observed at altitudes of (25.7;30.5;35.3;40.1) km because there are trends in water vapor and ozone concentrations at these altitudes. The La Niña phenomenon is used to see anomalies in water vapor and ozone concentrations from their normal state. La Niña phenomenon is observed based on the ONI index. We found that during La Niña, the water vapor concentration increased from its normal state while the ozone concentration decreased from its normal state. These two concentration values were used to find trends using Mann Kendall and Sen's Slope methods. We found that the trend of water vapor concentration is statistically significant while the trend of ozone concentration is the opposite.

Effect of Isopropanol on Optical Properties of Fe3O4/ZnO/Graphene Quantum Dots (GQDs) Nanocomposite

Sintha Widiawati, Astuti Astuti — Mon, 05 Aug 2024 00:00:00 +0700

This study aims to investigate the impact of isopropanol on the optical properties of the Fe₃O₄/ZnO/GQDs nanocomposite. The synthesis of Fe₃O₄ and ZnO nanoparticles was conducted using the coprecipitation method, followed by the synthesis of GQDs using the hydrothermal method with varying concentrations of isopropanol. Subsequently, the Fe₃O₄/ZnO nanocomposite was combined with GQDs synthesized using the sonication method. The amalgamation of magnetic and luminescent materials holds promise for applications in the biomedical field, particularly in bioimaging. XRD data analysis revealed crystal structure alterations attributed to the incorporation of carbon elements in both ZnO and Fe₃O₄. The TEM results indicated a particle size of 16.2 nm for the Fe₃O₄/ZnO/GQDs nanocomposite with a 10 ml isopropanol variation. Identified phases from the XRD analysis include Fe₃O₄, ZnO, and GQDs. UV-Vis spectroscopy detected distinctive absorbance peaks at wavelengths of 323.7 nm, 333.0 nm, 329.9 nm, and 323.9 nm. Moreover, the energy gap exhibited an increase with escalating concentrations of isopropanol in the GQDs. Photoluminescence analysis yielded robust, broad emission bands characterized by orange and red luminescence.

Annual and Interannual Rainfall Variability in Indonesia Using Empirical Orthogonal Function (EOF) Analysis and Its Response to Ocean-Atmosphere Dynamics

Melly Ariska, Suhadi Suhadi, Supari Supari, Muhammad Irfan, Iskhaq Iskandar — Thu, 15 Aug 2024 00:00:00 +0700

We investigate rainfall variability in Indonesia using the Empirical Orthogonal Function (EOF) method. The analysis starts by taking three main modes of EOF results, namely EOF1, EOF2, and EOF3. The EOF1 region is southern Indonesia, from southern Sumatra to Timor Island, parts of Kalimantan, parts of Sulawesi, and parts of Irian Jaya. The EOF2 region is located in northwestern Indonesia and includes the northern part of Sumatra and the northwestern part of Kalimantan. The EOF3 region covers Maluku. This study aims to analyze the annual and inter-annual variability of rainfall in anticipation of the threat of hydrometeorological disasters. Based on the correlation value of the principal component (PC) with the dipole mode index (DMI) and Niño3.4 index, it has a period similar to El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). Rainfall in Indonesia is very sensitive to sea surface temperature (SST) in the southeastern Indian Ocean and the central Pacific Ocean, which means that rainfall patterns in Indonesia can change significantly if SST in the region changes.

Simulation of the Effect of Dy3+ Dopant on the Mass Energy Absorption Coefficient and Relative Energy Response of TLD Made from Lithium Magnesium Borate Using MCNP

Nita Handayani, Dyon Novan Prawira, Fajar Arianto — Fri, 16 Aug 2024 00:00:00 +0700

Thermoluminescence dosimeter (TLD) is widely used as a personal and medical dosimeter. Several TLD materials show the characteristics of mass energy absorption coefficient and energy response relative to ICRU (International Commission on Radiation Units and Measurements) issue material as an equivalent material for human body soft tissue. This research aims to analyze the effect of Dy3+ dopant on the mass-energy absorption coefficient and relative energy response of Lithium Magnesium Borate (LMB) materials. The simulation was carried out using Monte Carlo N-Particle (MCNP) software. Calculations based on simulation and theoretical results will be compared statistically using paired t-tests. The study showed that adding a Dy3+ dopant to TLD material made of Lithium Magnesium Borate (LMB) only affected the mass-energy absorption coefficient and relative energy response for low radiation energy. Adding Dy3+ dopant increased the mass energy absorption coefficient and relative energy response in a reasonably small value. Based on these results, LMBDy3+ produces a better mass-energy absorption coefficient value for TLD materials. The results of the statistical tests show a significant difference in the mass energy absorption coefficient value. At the same time, there is no significant difference between the simulation results and theoretical calculations for the relative energy response.

Quasi-3D Geoelectrical Imaging as A New Application for Landslide Investigations: A Tunnel Case Induced by Blasting Activity

Rudi Cahyadi, Widodo Widodo — Fri, 30 Aug 2024 00:00:00 +0700

Landslides are a significant hazard in mountainous regions, especially when influenced by construction activities such as tunnel excavation. In this paper, we aim to conduct a slope stability analysis as a result of tunnel blasts using quasi-3D subsurface models based on resistivity values. The study site is a construction area for the Jakarta-Bandung High-Speed Train tunnel, located in a mountainous region undergoing drill-and-blast excavation. This excavation method makes the area susceptible to landslides, which pose a threat to settlements in the Padalarang subdistrict, West Bandung Regency, Indonesia. Data was collected along four lines in 2D, and the dipole-dipole array was used to enhance resolution. Data modeling was carried out using ResIPy v3.2.3 software to create 2D and quasi-3D subsurface models based on resistivity values. The study findings indicate that the study area exhibits three resistivity ranges: low resistivity (0-30 Ωm), medium resistivity (31-49 Ωm), and high resistivity (>50 Ωm). Utilizing quasi-3D imaging, we were able to identify the dimensions and presence of slip surfaces, which can be categorized as shallow (1.5-5 m) and deep (5-20 m) criteria. This study successfully applied the quasi-3D geoelectrical approach in a susceptible environment to detect potential landslide zones.

Subsurface Sediment Layer Analysis at the Dendam Tak Sudah Lake Flyover Construction Site in Bengkulu City Using the HV-Inv Method

Fri, 30 Aug 2024 00:00:00 +0700

Bengkulu City is situated within a subduction zone where the Indo-Australian and Eurasian tectonic plates converge, rendering the area highly susceptible to seismic activity. This study employs the microseismic method to assess seismic vulnerability and the subsurface rock structure at the Dendam Tak Sudah Lake Flyover Construction Site in Bengkulu City, which encompasses a swampy region. The microseismic method used was an inversion of the horizontal to vertical (H/V) spectral ratio (HV-Inv) for determining the dominant frequency (f₀), amplification factor (A₀), seismic sensitivity index (K_g), and shear wave velocity (V_s). The findings reveal that f₀ in the study area range from 2.16 to 7.53 Hz, A₀ vary from 0.40 to 3.79, and K_g values span from 0.03 to 6.04. The sedimentary layers exhibit an average thickness of 5-10 meters, with some locations showing significantly thicker sedimentary deposits. Notably, the highest seismic susceptibility is recorded at point T8. The V_s values range from 185.19 to 539.49 m/s, which are inversely proportional to the Kg values and indicate soil classifications varying from soft to medium. The overall seismic risk in the study area is moderate. These results offer key insights into geophysical and geological conditions in Bengkulu City, crucial for earthquake mitigation.