Indonesian Journal of Physics

Design of Neutron Activation and Radiography Facilities Based on DD Generator

Dian Adi Prastowo — 2023-12-29

Design and simulation of radiation facility using deuterium-deuterium (DD) neutron generator for neutron activation analysis (NAA) and radiography have been conducted by PHITS 3.30. A cylindrical DD neutron tube (E = 2.45 MeV isotropic, 5 x 10⁹/s) flux is surrounded by high-density polyethylene blocks which serve as the moderator. Within the moderator there are several cavities to perform neutron activation experiments. A 90 cm long beam tube is installed either radially or tangentially for radiography purposes. Monte Carlo simulations then calculate the thermal flux inside the cavities and on the end of the beam tube. The biggest thermal flux obtained in the activation chambers is about 1.95 x 10⁹/(cm².s) in the cavity closest to the source center. Radial beam tube delivers thermal flux of 7.86 x 10³/(cm².s), while tangential beam tube transports 1.86 x 10³/(cm².s). Although the thermal flux in the radial beam tube is higher, the fast neutron flux is also higher, about 9.60 x 10³/(cm².s). Tangential beam tube configuration can decrease fast neutron flux to only 2.00 x 10²/(cm².s). This result can serve as a preliminary study for the commisioning of radiation facilities based on compact, low-power neutron source.

Determination of Fractionation Scheme Based on Repair Effect Using Equivalent Uniform Dose (EUD) Model

Tiara Andrina Pratista — 2024-01-04

Radiotherapy treatment planning is required to obtain an optimal balance between delivering a high dose to target volume and a low dose to organ at risks. In this planning, it is also necessary to determine the appropriate fractionation scheme for each patient. One of the commonly used methods to determine the fractionation scheme is calculating the Normal Tissue Complication Probability (NTCP) and Tumor Control Probability (TCP) parameters. In this study, the Equivalent Uniform Dose (EUD) model is used to calculate NTCP and TCP. This model is based on a non-uniform dose distribution that is sensitive to the biological factors of cells. The biological factor examined in this research is the repair effect, which is the ability of cells to repair themselves after being radiated. Thus, the objective of this research is to determine the fractionation scheme based on NTCP calculations using the EUD model while taking into account the repair effect. The data used in this study were obtained from 10 patients with glioblastoma brain cancer in the form of cumulative DVH (dose-volume histogram) and total time of radiation. Based on the NTCP calculations, the average risk of organ complication for each patient appears to be close to zero, with a range of values from 2 x 10^-6% to 1 x 10^-1%. These results indicate that the treatment planning conducted is proven to be safe and there are no complications for the patients. Furthermore, based on the NTCP and TCP calculations, the best fractionation scheme is hypofractionation, which remains safe while considering the dose limit for each normal organ surrounding the target.

Analysis of the Effect of Tube Current, Slice Thickness, and Tube Voltage on Ct Scan Image Noise using the Noise Power Spectrum (NPS) Method

Anggita Ananda Kirei — 2024-01-04

This study was conducted to analyze CT scan images in order to determine the effect of tube current, slice thickness, and tube voltage on noise using the Noise Power Spectrum (NPS) method. Moreover, this study was also aimed to identify the optimal range of tube current, slice thickness, and tube voltage values to minimize noise formation in CT scan images while maintaining the safe dose for the patients. The research parameters included variations in tube current values with slice thickness variations, using tube voltages of 80 kV and 120 kV. The tube current (mAs) variations used were 150 mAs, 200 mAs, 250 mAs, 300 mAs, and 350 mAs, while the slice thickness variations were 0.8 mm, 1.6 mm, 3.2 mm, 4.8 mm, and 9.6 mm. A Phillips 16-slice access CT scan with a water phantom was utilized as the material for the research. The obtained image data were analyzed using ImQuest and ImageJ software. The results show that as the variations in tube current (mAs), slice thickness (mm), and tube voltage (mV) increase, the noise values decrease. This was demonstrated by the smallest area under the curve (AUC) values, which were 24.46 variance for the tube current variation at 120 kV and 3.57 variance for the slice thickness variation at 120 kV. Thus, to minimize the noise, it is recommended to increase the tube current, slice thickness, and tube voltage.

The Utilization and Optimization of Histogram of Oriented Gradients and Machine Learning in Face Recognition System

Muhammad Ervandy Rachmat — 2024-01-29

Computer science and technology development in recent years has experienced great developments. This time, some types of technology digitise almost everything related to human life, including facial recognition. In recent years, various methods for recognising human faces have developed. One of them is using the Histogram of Oriented Gradients (HOG). On this occasion, an image processing system will be designed to recognise human faces using Histograms of Oriented Gradients (HOG) and machine learning such as Convolutional Neural Networks (CNN) and Support Vector Machines (SVM). Detects the winking of the face, using computer-recognisable points in the eye area from 68 facial landmarks, so from these results, the distance between the upper and lower eyelids can be measured. If the distance (in pixels) is small enough, it can be interpreted as a wink. In addition, it is also limited by the distance of faces that can be detected to blink. In the end, if a recognised face blinks are detected, the time and date will be recorded. It will then open a solenoid lock using serial communication via Arduino Uno to become a security system. From 100 facial photos and 207 blink tests, 89.86% found that the computer could detect a "True Positive" wink. Besides, this facial recognition system's recommended tolerance parameter value is between 0.42 and 0.48.

Density Functional Theory Simulation of Iron-Montmorillonite as Carbon Dioxide Adsorber

Husni Ihsudha — 2024-01-29

Carbon dioxide (CO2) is a greenhouse gas that naturally keep the Earth^s surface temperature warm but currently the levels cause environmental problem such as climate change. Carbon capture and storage (CCS) technology is built to reduce CO2 gas emissions by binding carbon dioxide molecules and then storing them or utilising them as more useful products. In this study, simulations were carried out for the addition of iron (Fe) impurities as additional cation in montmorillonite to see the increase in the ability to bind carbon gas. Density Functional Theory calculations were carried out using additional corrections such as Van der Waals (vdW) and Hubbard-U. Here we got that Fe cation can help CO2 adsorbtion compare with other site without Fe atom by adding acid cite condition. But to adsorb CO2, the structure need initial process to swell the montmorillonite interlayer to certain optimum distance.

Magnetoteluric Modelling in High Noise of Low Frequency Signal

AGUS LAESANPURA — 2024-02-09

Magnetoteluric(MT) modelling geophysics in high noise areas is a challenging task. One part is the precious data for subsurface reconstruction, the other, the noise will a priori annoy the outcome. Through simulation and an example fact in the field, these two phenomena will be discussed. The simulation will propose the ideal model without and with noise, running on the Bostick inversion. Noise varies several schemas in two types of curves. Occam and Bostick algorithms will be used to run the inversion scheme. The trade of the advantages and disadvantages is then compared to a prior model in the field where MT data and geologic cross section are available. Two scenarios are available, one is to use data with treatment using available schema, and the other is to use data by cutting off the noise contaminant segment, and finally to see the resulted through 2D modelling process. The resultant shows the model use the ideal signal without noise through inversion resulting is a better than the other with a noisy signal experiencing treatment, notably in level shallow part. The geologic cross section and gravity model is available to support these results.