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- 저자 : Pham Nhu Viet Ha (검색결과 9 건)
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PHAM NHU VIET HA,김종경 한국원자력학회 2011 Nuclear Engineering and Technology Vol.43 No.6
In a previous study, the stochastic space-dependent kinetics model (SSKM) based on the forward stochastic model in stochastic kinetics theory and the Itô stochastic differential equations was proposed for treating monoenergetic space-time nuclear reactor kinetics in one dimension. The SSKM was tested against analog Monte Carlo calculations, however, for exemplary cases of homogeneous slab reactors with only one delayed-neutron precursor group. In this paper, the SSKM is improved and evaluated with more realistic and complicated cases regarding several delayed-neutron precursor groups and heterogeneous slab reactors in which the extraneous source or reactivity can be introduced locally. Furthermore, the source level and the initial conditions will also be adjusted to investigate the trends in the variances of the neutron population and fission product levels across the reactor. The results indicate that the improved SSKM is in good agreement with the Monte Carlo method and show how the variances in population dynamics can be controlled.
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HA, Pham Nhu Viet,KIM, Jong Kyung Atomic Energy Society of Japan 2011 Journal of nuclear science and technology Vol.48 No.2
<P>In previous studies, a simplified stochastic model (called the stochastic space-dependent kinetics model, SSKM) based on the forward stochastic model in the stochastic kinetics theory and the Itô stochastic differential equations was developed for the analysis of monoenergetic space-time nuclear reactor kinetics in one dimension. However, the behavior of the dynamic variations under a transient condition that plays a crucial role in operational and safety controls of nuclear power reactors has not been explicitly analyzed using this model. In this work, a numerical investigation is made using the SSKM in order to observe the random oscillations in population dynamics following various transients in subcritical and supercritical reactors. The results, which appear plausible on a physical basis, demonstrate that the behavior of the stochastic neutron and precursor distributions within a reactor can be induced using the SSKM.</P>
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Ha, Pham Nhu Viet,Kim, Jong-Kyung Korean Nuclear Society 2011 Nuclear Engineering and Technology Vol.43 No.6
In a previous study, the stochastic space-dependent kinetics model (SSKM) based on the forward stochastic model in stochastic kinetics theory and the Ito stochastic differential equations was proposed for treating monoenergetic space-time nuclear reactor kinetics in one dimension. The SSKM was tested against analog Monte Carlo calculations, however, for exemplary cases of homogeneous slab reactors with only one delayed-neutron precursor group. In this paper, the SSKM is improved and evaluated with more realistic and complicated cases regarding several delayed-neutron precursor groups and heterogeneous slab reactors in which the extraneous source or reactivity can be introduced locally. Furthermore, the source level and the initial conditions will also be adjusted to investigate the trends in the variances of the neutron population and fission product levels across the reactor. The results indicate that the improved SSKM is in good agreement with the Monte Carlo method and show how the variances in population dynamics can be controlled.
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Ha-Linh Quach,Thai Quang Pham,Ngoc-Anh Hoang,Dinh Cong Phung,Viet-Cuong Nguyen,Son Hong Le,Thanh Cong Le,Dang Hai Le,Anh Duc Dang,Duong Nhu Tran,Nghia Duy Ngu,Florian Vogt,Cong-Khanh Nguyen 대한의료정보학회 2022 Healthcare Informatics Research Vol.28 No.4
Objectives: Online misinformation has reached unprecedented levels during the coronavirus disease 2019 (COVID-19) pandemic. This study analyzed the magnitude and sentiment dynamics of misinformation and unverified information about public health interventions during a COVID-19 outbreak in Da Nang, Vietnam, between July and September 2020. Methods: We analyzed user-generated online information about five public health interventions during the Da Nang outbreak. We compared the volume, source, sentiment polarity, and engagements of online posts before, during, and after the outbreak using negative binomial and logistic regression, and assessed the content validity of the 500 most influential posts. Results: Most of the 54,528 online posts included were generated during the outbreak (n = 46,035; 84.42%) and by online newspapers (n = 32,034; 58.75%). Among the 500 most influential posts, 316 (63.20%) contained genuine information, 10 (2.00%) contained misinformation, 152 (30.40%) were non-factual opinions, and 22 (4.40%) contained unverifiable information. All misinformation posts were made during the outbreak, mostly on social media, and were predominantly negative. Higher levels of engagement were observed for information that was unverifiable (incidence relative risk [IRR] = 2.83; 95% confidence interval [CI], 1.33–0.62), posted during the outbreak (before: IRR = 0.15; 95% CI, 0.07–0.35; after: IRR = 0.46; 95% CI, 0.34-0.63), and with negative sentiment (IRR = 1.84; 95% CI, 1.23–2.75). Negatively toned posts were more likely to be misinformation (odds ratio [OR] = 9.59; 95% CI, 1.20–76.70) or unverified (OR = 5.03; 95% CI, 1.66–15.24). Conclusions: Misinformation and unverified information during the outbreak showed clustering, with social media being particularly affected. This indepth assessment demonstrates the value of analyzing online “infodemics” to inform public health responses.
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Tran Ha Thi Thanh,Dang Anh Kieu,Ly Duc Viet,Vu Hao Thi,Hoang Tuan Van,Nguyen Chinh Thi,Chu Nhu Thi,Nguyen Vinh The,Nguyen Huyen Thi,Truong Anh Duc,Pham Ngoc Thi,Dang Hoang Vu 아세아·태평양축산학회 2020 Animal Bioscience Vol.33 No.10
Objective: The rapid and reliable detection of the African swine fever virus (ASFV) plays an important role in emergency control and preventive measures of ASF. Some methods have been recommended by FAO/OIE to detect ASFV in clinical samples, including real-time polymerase chain reaction (PCR). However, mismatches in primer and probe binding regions may cause a false-negative result. Here, a slight modification in probe sequence has been conducted to improve the qualification of real-time PCR based on World Organization for Animal Health (OIE) protocol for accurate detection of ASFV in field samples in Vietnam. Methods: Seven positive confirmed samples (four samples have no mismatch, and three samples contained one mutation in probe binding sites) were used to establish novel real-time PCR with slightly modified probe (Y = C or T) in comparison with original probe recommended by OIE. Results: Both real-time PCRs using the OIE-recommended probe and novel modified probe can detect ASFV in clinical samples without mismatch in probe binding site. A high correlation of cycle quantification (Cq) values was observed in which Cq values obtained from both probes arranged from 22 to 25, suggesting that modified probe sequence does not impede the qualification of real-time PCR to detect ASFV in clinical samples. However, the samples with one mutation in probe binding sites were ASFV negative with OIE recommended probe but positive with our modified probe (Cq value ranked between 33.12-35.78). Conclusion: We demonstrated for the first time that a mismatch in probe binding regions caused a false negative result by OIE recommended real-time PCR, and a slightly modified probe is required to enhance the sensitivity and obtain an ASF accurate diagnosis in field samples in Vietnam.
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Re-evaluations for SINBAD Experiments Using ENDF/B-VII, JEFF-3.1, and JENDL-3.3
김종경,Pham Nhu Viet Ha,신창호,김도헌,이영욱 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
SINBAD (Shielding Integral Benchmark Archive Database) started in 1996 as a joint project of the OECD/NEA Data Bank (Organization for Economic Cooperation and Development, Nuclear Energy Agency Data Bank) and ORNL/RSICC (Oak Ridge National Laboratory, Radiation Safety Information Computational Center). It contains a variety of experiments concerning reactor shielding, fusion blanket neutronics, and accelerator shielding that are useful to verify and validate radiation shielding codes as well as nuclear data libraries. In this work, re-evaluation of SINBAD experiments has been conducted by using the MCNPX code with recently released nuclear data libraries, ENDF/B-VII, JEFF-3.1, and JENDL-3.3. The MCNPX calculations for several typical problems of SINBAD reactor shielding, fusion neutronics, and accelerator shielding were carried out and validated through comparing with available experimental data. It is found that there was reasonable agreement between the calculational and experimental results. Hence, ENDF/B-VII, JEFF-3.1, and JENDL-3.3 are strongly recommended to be used for validating the new developed radiation shielding methods and codes.
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강상묵,신창호,Pham Nhu Viet Ha,최창일,김종경,김용균 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.22
A computed radiography (CR) system using reusable image plates (IPs) offers a convenient and reliable way to replace a conventional film-screen system for non-destructive testing field. The ability of radiography to detect a defect in welded objects depends on the procedure and embraces several factors such as the measurement conditions, the image plate type/class, the radiation energy, the radiation type, and the source-to-image plate distance. Also, the ability of images to detect a flaw decreases with increasing object thickness. In the study, images of welded objects were acquired with a CR system manufactured by FUJI by using Selenium-75, Iridium-192, and X-ray with and were obtained through MCNP5 simulations under the same conditions as the given experiments conditions.
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Vu, Thanh Mai,Hartanto, Donny,Ha, Pham Nhu Viet Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.7
A small power ADS design using thorium oxide and diluent matrix reprocessed fuel is proposed for a high transmutation rate, small reactivity swing, and strong safety features. Two fuel matrices (CERCER and CERMET) and different recycled fuel compositions recovered from UO<sub>2</sub> spent fuels with 45 GWd/tU and 60 GWd/tU burnup were investigated to determine the suitable fuel for the ADS. It was found that the transmutation of each isotope depends on TRU initial loading amount. After examining the cores, the results show that CERCER fueled ADS has a negative coolant void reactivity (CVR) and a smaller radiotoxicity at discharge compared to that of CERMET core. It implies that CERCER fuel has enhanced safety features and more flavor in terms of radiotoxicity management. To increase fuel utilization and core operation efficiency, a simple assembly shuffling pattern for the CERCER fueled ADS is also proposed. Eigenvalue and burnup calculations were conducted using Serpent 2 with ENDF/B-VII.0 library in both kcode and external source modes, and it indicates that the results of transmutation analyses obtained by kcode only is reliable to discuss the transmutation potential of ADS. Burnup calculation with the fixed-source mode is essential to be used for more practical results of the transmutation by ADS.
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