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TRƯỜNG ĐẠI HỌC KHOA HỌC TỰ NHIÊN, ĐẠI HỌC QUỐC GIA THÀNH PHỐ HỒ CHÍ MINH

KHOA VẬT LÝ - VẬT LÝ KỸ THUẬT

BỘ MÔN VẬT LÝ HẠT NHÂN - NGÀNH KỸ THUẬT HẠT NHÂN - NGÀNH VẬT LÝ Y KHOA

Le Thi Ngoc Trang, Huynh Dinh Chuong, Tran Thien Thanh

Journal of Radioanalytical and Nuclear Chemistry (2020)

Abstract:

In this study, the optimization of the p-type HPGe detector model has been performed to improve the accuracy of Monte Carlo simulation in calculating full energy peak efficiency. The optimized detector model was validated by comparison of simulated efficiencies with experimental efficiencies for measurement configurations of point-like sources at various distances from the detector surface and cylindrical sources on the detector surface. The obtained results showed an excellent agreement between the simulated and experimental efficiencies with relative deviations of less than 4% in the energy range from 53 to 1847 keV.

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On the Bohr-Sommerfeld quantization condition and assault frequency in a semiclassical model for α decay

Le Hoang Chien, Nguyen Tri Toan Phuc

Nuclear Physics A 1018 (2022) 122373

Abstract:

We study the impacts of the Bohr-Sommerfeld quantization condition and the assault frequency on the α decay half-life within the semiclassical model. The potential between the α particle and daughter nucleus is calculated by the double-folding model using the CDM3Y3 density-dependent nucleon-nucleon interaction with a finite-range exchange term. We show that the proper implementation of the Bohr-Sommerfeld condition leads to a considerable change of the calculated α decay half-life with certain forms of potential. We also propose an alternative treatment for the assault frequency based on the generalized oscillator potential. This description of assault frequency considerably improves the agreement between the calculated α decay half-lives and the experimental data.

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Non-destructive evaluation of thickness of material plates through Compton back-scattering technique using Si(Li) detector

Huynh Dinh Chuong, Nguyen Duy Thong, Vo Hoang Nguyen, Le Hoang Minh, Nguyen Thi Truc Linh, Phan Long Ho, Tran Thien Thanh, Chau Van Tao

Radiation Physics and Chemistry (2022), 109978

Abstract:

This study aims to develop the system for the non-destructive evaluation of the thickness of material plates based on the Compton back-scattering technique using a Si(Li) detector and 241Am radioactive sources. The calibration curve is constructed based on the areas under the Compton scattering peak obtained from the measurements of reference samples. This calibration curve is used to determine the saturation thickness, the maximum measurable thickness (MMT) with the desired accuracy, and the unknown thickness of a sample. To validate the reliability of the system, we have performed thickness measurements for seventeen aluminum samples with different thicknesses in the range of 4.40–21.07 mm. The samples are measured seven times, except for two samples with thicknesses of 11.52 mm and 14.98 mm up to twenty times. The Pearson's correlation coefficient between the reference and measured thicknesses presented a strong positive correlation. The average relative deviation between the reference and measured thicknesses is less than 1%.

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Natural Radionuclides in Rice Soils in the Mekong Delta Region, Vietnam: Health Risk, Transfer to Rice, and Long-Term Accumulation in Topsoil

 Van Thang Nguyen, Binh An Le, Nguyen Phong Thu Huynh & Cong Hao Le 

Water, Air, & Soil Pollution volume 232, Article number: 354 (2021)

Abstract:

In the world, many studies have focused on the natural radioactivity in agricultural soils and food crops and the transfers of radionuclides between two components. However, the influence of long-term agricultural practices on the activity concentrations of radionuclides in the soils remains unclear. On the other hand, the soil-to-plant transfer factors of radionuclides for a specific plant type are different between the regions of the world. In this study, activity concentrations of natural radionuclides in 16 rice and corresponding soil samples in the Mekong Delta region of Vietnam were measured by a gamma spectrometer with a high purity germanium detector. The accumulation rates of radionuclides were predicted by using a model based on the balance between input and output rates of radionuclides in the topsoil. Based on the analysis of radionuclides in soil and rice samples, the average values of TF estimated for 40 K, 226Ra, 232Th, and 238U were 4.2 ± 0.5 × 10−2, 3.2 ± 0.6 × 10−2, 4.6 ± 1.1 × 10−3, and 1.9 ± 0.4 × 10−2, respectively. For long-term assessment, the annual rates 39 ± 2 Bq kg−1 year−1, 26.8 ± 2 mBq kg−1 year−1, − 418 ± 34 mBq kg−1 year−1, and − 358 ± 30 mBq kg−1 year−1 were estimated for 40 K, 226Ra, 232Th, and 238U, respectively. From the results of this study, it is evident that irrigation system is the main factor that caused accumulations of radionuclides in the soil. Water leaching and rice uptake were two processes that were responsible for the rejection of radionuclides from the soil. The accumulation rates of radionuclides are therefore controlled by changing the cultivation conditions.

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Huynh Dinh Chuong, Truong Thanh Sang, Hoang Duc Tam

Radiation Physics and Chemistry 179 (2021) 109216

Abstract:

In this study, we propose a new approach for determining the density of liquid based on the gamma transmission technique in combination with Monte Carlo simulation. This approach involves analysing the sensitivity of the measurement whilst changing the diameter of a tube containing a liquid and then based on the simulated data to construct a linear calibration curve. The proposed approach is validated by measuring the density of nine liquids with a density in the range of 0.6–2.0 g cm−3 for four various diameters of the tubes. The results showed the percent di erence between the measured and the reference densities of less than 5% for most measurements, and the relative uncertainty of measurements of less than 4%.

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Modeling Respiratory Signals by Deformable Image Registration on 4DCT Lung Images

Pham The Bao, Hoang Thi Kieu Trang, Tran Anh Tuan, Tran Thien Thanh and Vo Hong Hai

Hindawi, BioMed Research International Volume 2021, Article ID 6654247, 15 pages

Abstract:

The lung organ of human anatomy captured by a medical device reveals inhalation and exhalation information for treatment and monitoring. Given a large number of slices covering an area of the lung, we have a set of three-dimensional lung data. And then, by combining additionally with breath-hold measurements, we have a dataset of multigroup CT images (called 4DCT image set) that could show the lung motion and deformation over time. Up to now, it has still been a challenging problem to model a respiratory signal representing patients’ breathing motion as well as simulating inhalation and exhalation process from 4DCT lung images because of its complexity. In this paper, we propose a promising hybrid approach incorporating the local binary pattern (LBP) histogram with entropy comparison to register the lung images. The segmentation process of the left and right lung is completely overcome by the minimum variance quantization and within class variance techniques which help the registration stage. The experiments are conducted on the 4DCT deformable image registration (DIR) public database giving us the overall evaluation on each stage: segmentation, registration, and modeling, to validate the effectiveness of the approach.

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