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Thong L.D.,Ho Chi Minh City Institute of Physics | van Hung T.,Research and Development Center for Radiation Technology | Thu Huong N.T.,Vietnam National University, Hanoi | Bang H.H.,Vietnam National University, Hanoi
Astrophysics | Year: 2010

The variation of the fine-structure constant α = e2 th{stroke}c can be probed by comparing the wavelength of atomic transitions from the redshift of quasars in the Universe and laboratory over cosmological time scales t ~ 1010 yr. After a careful selection of pairs of lines, the Thong method with a derived analytical expression for the error analysis was applied to compute the α variation. We report a new constraint on the variation of the fine-structure constant based on the analysis of the CIV, NV, MgII, AlIII, and SiIV doublet absorption lines. The weighted mean value of the variation in α derived from our analysis over the redshift range 0.4939 ≤ z ≤ 3.7 is = (0.09 ± 0.07)×10-5. This result is three orders of magnitude better than the results obtained by earlier analysis of the same data on the constraint on Δα/α. © 2010 Springer Science+Business Media, Inc.


Van Hung T.,Research and Development Center for Radiation Technology
Journal of Radioanalytical and Nuclear Chemistry | Year: 2010

A modified method has been developed for the α determination in the 1/E 1+α epithermal neutron spectrum of reactor. It is based on the Cd-covered and without Cd-covered irradiations of two monitors. This method was applied to determine the α value in the channels of Dalat reactor and the results were compared with those obtained by the other methods. It appeared that the results of the modified method were in quite good agreement with those of other methods. It also showed that the modified method was simple in practical uses and a good application in the experiment of α determination in the reactor irradiation channels. © 2010 Akadémiai Kiadó, Budapest, Hungary.


Van Hung T.,Research and Development Center for Radiation Technology
Journal of Radioanalytical and Nuclear Chemistry | Year: 2010

The α-factor is a measure of the epithermal neutron flux deviation from the ideal distribution 1/E, where E is neutron energy. It defends on the position of the irradiation channel in reactor. A determination method of the α-factors in irradiation channels of Dalat reactor is presented by fitting the epithermal neutron spectrum obtained from the calculation using MCNP code. The fitting α-values were compared to those by experiment used the "Cd-ratio" method with monitors 197Au-94Zr and 197Au-64Zn. It shows that the α-values calculated from neutron spectra agree well with experimental ones. The difference between both data is about 6%. © 2010 Akadémiai Kiadó, Budapest, Hungary.


Hanh T.T.,Research and Development Center for Radiation Technology | Van Phu D.,Research and Development Center for Radiation Technology | Thu N.T.,Research and Development Center for Radiation Technology | Quoc L.A.,Research and Development Center for Radiation Technology | And 2 more authors.
Carbohydrate Polymers | Year: 2014

Silver nanoparticles (AgNPs) with diameter about 12 nm were immobilized on the surface of cotton fabrics by γ-irradiation of fabrics in the AgNO 3 chitosan solution. Effects of absorbed dose, concentration of AgNO3 solution on immobilization of the AgNPs on fabrics were investigated. The optimal dose was selected to be 13.8 kGy and the suitable concentration of AgNO3 was 1.5 mM in 1% chitosan solution. The content of AgNPs on fabrics was of 1696 ± 80 mg/kg for these conditions. The presence of AgNPs on fabrics was confirmed from scanning electron microscopy (SEM) images and X ray diffraction (XRD) patterns. The antibacterial activity of AgNPs/cotton fabrics after 40 washings against Staphylococcus aureus and Escherichia coli was found to be 99.99%. In addition, the AgNPs fabrics were innoxious to the skin (k = 0) after 1, 5, 10, 20, 30 and 40 washings by skin-irritation testing to animal (rabbit). © 2013 Elsevier B.V. All rights reserved.


Van Hung T.,Research and Development Center for Radiation Technology
Kerntechnik | Year: 2013

Age-dependent effective dose for external exposure to photons uniformly distributed in air were calculated. Firstly, organ doses were calculated with a series of age-specific MIRD-5 type phantoms using the Monte Carlo code MCNP. The calculations were performed for mono-energetic photon sources with source energies from 10 keV to J MeV and for phantoms of newborn, 1, 5, 10, and 15 years-old and adult. Then, the effective doses to the different age-phantoms from the mono-energetic photon sources were estimated based on the obtained organ doses. From the calculated results, it is shown that the effective doses depend on the body size; the effective doses in younger phantoms are higher than those in the older phantoms, especially below 100 keV. © Carl Hanser Verlag, München.


Van Hung T.,Research and Development Center for Radiation Technology | Khac An T.,Research and Development Center for Radiation Technology
Applied Radiation and Isotopes | Year: 2010

By using MCNP code and ethanol-chlorobenzene (ECB) dosimeters the simulations and measurements of absorbed dose distribution in a tote-box of the Cobalt-60 irradiator, SVST-Co60/B at VINAGAMMA have been done. Based on the results Dose Uniformity Ratios (DUR), positions and values of minimum and maximum dose extremes in a tote-box, and efficiency of the irradiator for the different dummy densities have been gained. There is a good agreement between simulation and experimental results in comparison and they have valuable meanings for operation of the irradiator. © 2010 Elsevier Ltd. All rights reserved.


PubMed | Research and Development Center for Radiation Technology
Type: | Journal: Carbohydrate polymers | Year: 2013

Silver nanoparticles (AgNPs) with diameter about 12 nm were immobilized on the surface of cotton fabrics by -irradiation of fabrics in the AgNO3 chitosan solution. Effects of absorbed dose, concentration of AgNO3 solution on immobilization of the AgNPs on fabrics were investigated. The optimal dose was selected to be 13.8 kGy and the suitable concentration of AgNO3 was 1.5mM in 1% chitosan solution. The content of AgNPs on fabrics was of 1,696 80 mg/kg for these conditions. The presence of AgNPs on fabrics was confirmed from scanning electron microscopy (SEM) images and X ray diffraction (XRD) patterns. The antibacterial activity of AgNPs/cotton fabrics after 40 washings against Staphylococcus aureus and Escherichia coli was found to be 99.99%. In addition, the AgNPs fabrics were innoxious to the skin (k=0) after 1, 5, 10, 20, 30 and 40 washings by skin-irritation testing to animal (rabbit).


PubMed | Research and Development Center for Radiation Technology
Type: Journal Article | Journal: Journal of radioanalytical and nuclear chemistry | Year: 2015

A modified method has been developed for the determination in the 1/


PubMed | Research and Development Center for Radiation Technology
Type: Journal Article | Journal: Journal of radioanalytical and nuclear chemistry | Year: 2015

The neutron temperature is a characteristic parameter in irradiation channels of reactor. For nuclides which have resonances in the thermal neutron energy range, their Westcott g-factors are different from unity. The values of g-factors and cross-sections of (n, ) reaction of these nuclides are temperature dependence. The standard energy for tabulation of thermal neutron cross-section (


Binh D.,Research and Development Center for Radiation Technology | Pham Thi Thu Hong,Research and Development Center for Radiation Technology | Nguyen Ngoc Duy,Research and Development Center for Radiation Technology | Nguyen Thanh Duoc,Research and Development Center for Radiation Technology | Nguyen Nguyet Dieu,Research and Development Center for Radiation Technology
Radiation Physics and Chemistry | Year: 2012

The formation of carboxymethyl starch (CMS) nanogel with 50nm less particle size was carried out through a radiation crosslinked process on the electron beam (EB) linear accelerator. Changes of intrinsic viscosities and weight averaged molecular weight in the CMS concentration, which ranged from 3 to 10mgml -1 in absorbed doses were investigated. There were some new peaks in the 1H NMR spectra of CMS nanogel compared with those of CMS polymer. These results were anticipated that the predominant intramolecular crosslinking of dilute CMS aqueous solution occurred while being exposed to a short intense pulse of ionizing radiation. Hydrodynamic radius (often called particle size, R h) and distribution of particle size were measured by a dynamic light scattering technique. The radiation yield of intermolecular crosslinking of CMS solution was calculated from the expression of G x (Charlesby, 1960; Jung-Chul, 2010). The influence of the "size effect" was demonstrated by testing culture of Lactobacillus bacteria on MRS agar culture medium containing CMS nanogel and polymer. Results showed that the number of Lactobacillus bacteria growing on nanogel containing culture medium is about 170cfu/ml and on polymer containing culture medium is only 6cfu/ml. © 2012 .

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