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  • Article


  • Authors: Nguyen, Van Hung; Nguyen, Bao Trung; Nguyen, Cong Toan; Ha, Dang Khoa (2017)

  • Debye-Waller factors (DWFs) of metallic Cu (fcc crystal) in X-ray absorption fine structure (XAFS) presented in terms of cumulant expansion have been studied using the anharmonic correlated Debye model (ACDM). This ACDM is derived using the many-body perturbation approach and the anharmonic effective potential that includes the first shell near neighbor contributions to the vibration between absorber and backscatterer atoms. Analytical expressions of three first XAFS cumulants of Cu have been derived involving more information of phonon-phonon interactions taken from integration over the first Brillouin zone. Morse potential is assumed to describe the single-pair atomic interaction. Numerical results for Cu using the present ACDM show their good agreement with experiment and with th...

  • Article


  • Authors: Nguyen, Van Hung; Nguyen, Cong Toan; Hoang, Thi Khanh Giang (2010)

  • Analytical expressions for the ratio of the root mean square fluctuation in atomic positions on the equilibrium lattice positions and the nearest neighbor distance and the mean melting cgryes of bcc binary alloys haye been derived. This melting curve provides information on Lindemann's melting temperatures of binary alloys with respect to any proportion of constituent elements and on their euctectic points. Numerical results for some bcc binary alloys are found to be in agreement with experiment.

  • Article


  • Authors: Nguyen, Van Hung; Trinh, Thi Hue; Nguyen, Ba Duc (2015)

  • In this work, Morse potential parameters of bcc crystals have been calculated based on the calculation of volume per atom and atomic number in each elementary cell, as well as the energy of sublimation, the compressibility and the lattice constant. They are used for studying the anharmonic interatomic effective potential, local force constant in XAFS (X-ray Absorption Fine Structure) theory. Numerical results for Fe, W and Mo are found to be in good agreement with experiment and with those of other theories.

  • Article


  • Authors: Nguyen, Van Hung; Trinh, Thi Hue; Nguyen, Bao Trung; Nguyen, Cong Toan (2017)

  • Anharmonic correlated Debye model is derived for Debye-Waller factors of bcc (body-centered cubic) crystals presented in terms of cumulant expansion up to the fourth order. The many-body effects are taken into account in the present one-dimensional model based on the anharmonic effective potential that includes interactions of absorber and backscatterer atoms with their first shell near neighbors, where Morse potential is assumed to describe the single-pair atomic interaction. Analytical expressions for dispersion relation, correlated Debye frequency and temperature and four first temperature-dependent XAFS (X-ray absorption fine structure) cumulants of bcc crystals have been derived using the many-body perturbation approach. Numerical results for W are found to be in good agreement...

  • Article


  • Authors: Nguyen, Van Hung; Duong, Anh Tuan; Trinh, Duc Thien; Nguyen, Dang Phu; Danh, Bich Do; Pham, Van Vinh (2012)

  • CdTe quantum dots dispersed in water were prepared successfully by the microwave irradiation method. The influence of the pH value of the solution precursor, irradiation time and microwave power on the structure, size and optical properties of CdTe quantum dots was investigated. The fluorescence of CdTe quantum dots studies were illustrated that the samples which were synthesized at pH value of 7 exhibited the best fluorescence. The absorption, fluorescence spectra and TEM images showed that the microwave power and the irradiation time influenced significantly on the size of CdTe quantum dot as well as their optical properties. The fluorescence spectra were red-shift with the increase of the irradiation time and microwave power.

  • Article


  • Authors: Bui, Van Loat; Nguyen, Van Hung; Hoang, Sy Minh Phuong (2010)

  • At present, thickness measurement of materials based on effect of backscattering gamma-ray has been widely used in industry in our country. The report presented research in measuring thickness of some materials such as paper, plastic, aluminum and steel with using the dedicated system of MYO-101, having scintillation detector of YAP(Ce) and gamma-ray of 60 keV of Am-241 source, by Monte-Carlo simulation using the code of MCNP. The simulation was checked by experimental measurements. The results were shown that they were in accordance with the range of error. This research has been useful for training activities with a view of human resowces development in the field of application of nuclear techni.que in industry in Vietnam.

  • Article


  • Authors: Le, Huynh My Van; Nguyen, Van Hung (2014)

  • In this paper, we study the systems of generalized quasiequilibrium problems which includes as special cases the generalized vector quasi-equilibrium problems, vector quasiequilibrium problems, and establish the existence results for its solutions by using fixed-point theorem. Moreover, we also discuss the closedness of the solution sets of systems of generalized quasiequilibrium problems. As special cases, we also derive the existence results for vector quasiequilibrium problems and vector quasivariational inequality problems. Our results are new and improve recent existing ones in the literature.

  • Article


  • Authors: Nguyen, Van Hung; Phan, Thanh Kieu (2013)

  • In this paper we establish sufficient conditions for the solution mappings of parametric generalized vector quasiequilibrium problems to have the stability properties such as lower semicontinuity, upper semicontinuity, Hausdorff lower semicontinuity, continuity, Hausdorff continuity and closedness. The results presented in the paper improve and extend the main results of Kimura-Yao [J. Global Optim. 138, (2008) 429-- 443], Kimura-Yao [Taiwanese J. Math., 12, (2008) 649--669] and Anh-Khanh [J. Math. Anal. Appl., 294, (2004) 699--711]. Some examples are given to illustrate our results.