Browsing by Author Nguyen, Van Hung

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Showing results 1 to 20 of 26
  • 180.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Nguyen, Bao Trung (2006)

  • An anharmonic correlated Debye model has been derived for vibrational amplitudes in the X-ray Absorption Fine Structure (XAFS). The model includes anharmonic effects based on Morse potential parameters. Analytical expression for Debye-Waller factor or second cumulant for different atomic shells has been derived. Numerical results for Cu approach those obtained by the anharmonic Einstein model. Both they contain zero-point contribution at low temperatures and linearly depend on the temperature at high temperatures as the classical limit values. They reflect the experimental results.

  • 4076-97-8103-1-10-20171016.pdf.jpg
  • 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. N...

  • 24.pdf.jpg
  • 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 ...

  • 170.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Le, Thi Thuy Hau; Tong, Sy Tien (2007)

  • A new procedure for calculation and analysis of XAFS (X-ray Absorption Fine Structure) cumulants of hep crystals containing dopant atom has been derived based on quantum statistical theory with generalized anharmonic correlated Einstein model. Analytical expressions for effective local force constants, correlated Einstein frequency and temperature, first cumulant or net thermal expansion, second cumulant or Debye Waller factor and third cumulant of hep crystals containing dopant atom have been derived. Morse potential parameters of pure crystals and those with dopant included in the derived expressions have been calculated. Numerical results for Zn doped by Cd are found to be in good ...

  • 123.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Ngo, Trong Hai; Tong, Sy Tien; Le, Hai Hung (2009)

  • Anharmonic effective potential, effective local force constant, thermal expansion coefficient, three leading cumulants, and EXAFS (Extended X-ray Absorption Fine Structure) of hep crystals have been studied. Analytical expressions for these quantities have been derived. Numerical calculations have been carried out for Zn and Cd. They show a good agreement with experiment results measured at HASYLAB (DESY, Germany) and unnegligible anharmonic effects in the considered quantities.

  • 102.pdf.jpg
  • 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.

  • 115.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Nguyen, Cong Toan; Nguyen, Bao Trung; Ngo, Hoang Giang (2008)

  • Analytical expressions for the Morse potential parameters of diamond crystals have been derived. They contain the energy of sublimation, the compressibility and the lattice constant. Numerical calculations have been carried out for Si and Sn, and the result reflect fundamental calcultion of the anharmonic correlated effective potential parameters have been used for calculation of the anharmonic correlated effective potentials of these crystals in XAFS theory showing clearly anharmonic effects.

  • 237.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Dao, Xuan Viet (2003)

  • A new procedure for calculation of the Morse potential parameters of hexagonal closed packed (hcp) crystals has been developed using the energy of sublimation, the compressibility and the lattice constant. The derived equation of state and the elastic constants computed using the obtained Morse parameters agree with the experimental ones. This shows that the Morse dunction can be applied validly to the problems involving any type of deformation and atomic interaction in the hcp crystals.

  • 49.pdf.jpg
  • 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.

  • 3.pdf.jpg
  • 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.

  • 201.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Nguyen, Thi Thu Hoai; Le, Hai Hung (2004)

  • A new procedure for calculation and evaluation of XAFS cumulants of fee crystals containing impurity atom has been developed based on the quantum statistical theory with correlated Einstein model. Analytical expressions for the effective local force constants, correlated Einstein frequency and temperature, first cumulant or net thermal expansion, second cumulant or Debye Waller factor and third cumulant of fee crystals containing impurity atom have been derived. Morse potential parameters of pure crystals and those with impurity included in the derived expressions have been calculated. Numerical results for Cu. Ni. Ni-Cu are found to be in good agreement with experiment

  • 62.pdf.jpg
  • 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...

  • document(38).pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Bui, Thi Viet Ha; Dinh, Thuy Hang (2016)

  • An efficient method was established for isolation of bifidobacteria from fecal samples of breast-fed infants. The method was based on the combination of Hungate technique applied on anoxic semi-liquid agar tubes, instead of double layer agar plates. Four growth media including BFM, BIM25, MRS and 385 were compared for the isolation efficiency on the basis of Hungate technique. Thus, among 30 isolates obtained from fecal samples of 14 breast fed infants of different ages under 1 year only eight bifidobacteria-like isolates were selected based on cell morphology and fermentation motif. It is revealed that Hungate technique with the use of anaerobic MRS and BFM media was more efficient f...

  • 96.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Bui, Van Loat (2009)

  • The paper resented the results of assessing internal dose for 131I by the direct method for Vietnamese objects that was issued in the Intercomparison Program of IAEA. The results on experimental measurements, caculating intake (I) or 131I to thyroid by the specializing system for measuring thyroid activity, and committed effective dose E(50) using the specializing code of LUDEP 2.0 were shown that the results carrying out at the Nuclear Research Institute were goof and were in accordance with the those of the authors in other laboratories in the world.

  • 117.pdf.jpg
  • 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 n...

  • 122.pdf.jpg
  • Article


  • Authors: Khong, Cat Cuong; Trinh, Duc Thien; Pham, Thu Nga; Nguyen, Van Minh; Nguyen, Van Hung (2009)

  • In this article, we report on the preparation of CdSe quantum dots (QDs) by sol-gel method and their optical properties. The average size of QDs is also estimated by using various ways, such as the Scherer’s formula. The Effros-Brus-Kayanum a's theoretical expression, TEM etc. The TEM images of samples show that the mean sizes of QDs are 4 nm. The mean sizes of QDs are smaller than that of other methods and arranging from 2 to 3.6 nm.

  • 132.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Tran, Trung Dung; Nguyen, Cong Toan (2006)

  • A new procedure for description and calculation of th EXAFS (Extended X-ray Absorption Fine Structure) cumulants for fee crystals containing an abitrary number n of dopant atoms have been developed. Analytical expressions for the l 8t, 2nd and 3rd cumulants have been derived.They depend on the number of dopant atoms and approach those derived by anharmonic correlated Einstein model, if all dopant atoms are taken out or replacing all the host atoms. Numerical results for Cu doped by Ni atoms based on the Morse potential show significant dependence of thermodynamic parameters of the substance on the number of dopant atoms and a reasonable agreement with experiment.

  • 209.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Tran, Trung Dung; Nguyen, Cong Toan (2004)

  • A new procedure for description and calculation of the interaction potential and force constants for fee crystals containing an arbitrary number n of impurity atoms have been developed. Analytical expressions for the effective atomic interaction potential, the single-bond and effective spring constants have been derived. They depend on the number of the impurity atoms and approach those derived by using anharmonic correlated Einstein model, if all the impurity atoms are taken out or they replace all the host atoms. Numerical results for Ni doped by Cu atoms show significant changes of the interact on potential and spring constants of the substance if the number of impurity ato...

Browsing by Author Nguyen, Van Hung

Jump to: 0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
or enter first few letters:  
Showing results 1 to 20 of 26
  • 180.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Nguyen, Bao Trung (2006)

  • An anharmonic correlated Debye model has been derived for vibrational amplitudes in the X-ray Absorption Fine Structure (XAFS). The model includes anharmonic effects based on Morse potential parameters. Analytical expression for Debye-Waller factor or second cumulant for different atomic shells has been derived. Numerical results for Cu approach those obtained by the anharmonic Einstein model. Both they contain zero-point contribution at low temperatures and linearly depend on the temperature at high temperatures as the classical limit values. They reflect the experimental results.

  • 4076-97-8103-1-10-20171016.pdf.jpg
  • 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. N...

  • 24.pdf.jpg
  • 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 ...

  • 170.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Le, Thi Thuy Hau; Tong, Sy Tien (2007)

  • A new procedure for calculation and analysis of XAFS (X-ray Absorption Fine Structure) cumulants of hep crystals containing dopant atom has been derived based on quantum statistical theory with generalized anharmonic correlated Einstein model. Analytical expressions for effective local force constants, correlated Einstein frequency and temperature, first cumulant or net thermal expansion, second cumulant or Debye Waller factor and third cumulant of hep crystals containing dopant atom have been derived. Morse potential parameters of pure crystals and those with dopant included in the derived expressions have been calculated. Numerical results for Zn doped by Cd are found to be in good ...

  • 123.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Ngo, Trong Hai; Tong, Sy Tien; Le, Hai Hung (2009)

  • Anharmonic effective potential, effective local force constant, thermal expansion coefficient, three leading cumulants, and EXAFS (Extended X-ray Absorption Fine Structure) of hep crystals have been studied. Analytical expressions for these quantities have been derived. Numerical calculations have been carried out for Zn and Cd. They show a good agreement with experiment results measured at HASYLAB (DESY, Germany) and unnegligible anharmonic effects in the considered quantities.

  • 102.pdf.jpg
  • 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.

  • 115.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Nguyen, Cong Toan; Nguyen, Bao Trung; Ngo, Hoang Giang (2008)

  • Analytical expressions for the Morse potential parameters of diamond crystals have been derived. They contain the energy of sublimation, the compressibility and the lattice constant. Numerical calculations have been carried out for Si and Sn, and the result reflect fundamental calcultion of the anharmonic correlated effective potential parameters have been used for calculation of the anharmonic correlated effective potentials of these crystals in XAFS theory showing clearly anharmonic effects.

  • 237.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Dao, Xuan Viet (2003)

  • A new procedure for calculation of the Morse potential parameters of hexagonal closed packed (hcp) crystals has been developed using the energy of sublimation, the compressibility and the lattice constant. The derived equation of state and the elastic constants computed using the obtained Morse parameters agree with the experimental ones. This shows that the Morse dunction can be applied validly to the problems involving any type of deformation and atomic interaction in the hcp crystals.

  • 49.pdf.jpg
  • 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.

  • 3.pdf.jpg
  • 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.

  • 201.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Nguyen, Thi Thu Hoai; Le, Hai Hung (2004)

  • A new procedure for calculation and evaluation of XAFS cumulants of fee crystals containing impurity atom has been developed based on the quantum statistical theory with correlated Einstein model. Analytical expressions for the effective local force constants, correlated Einstein frequency and temperature, first cumulant or net thermal expansion, second cumulant or Debye Waller factor and third cumulant of fee crystals containing impurity atom have been derived. Morse potential parameters of pure crystals and those with impurity included in the derived expressions have been calculated. Numerical results for Cu. Ni. Ni-Cu are found to be in good agreement with experiment

  • 62.pdf.jpg
  • 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...

  • document(38).pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Bui, Thi Viet Ha; Dinh, Thuy Hang (2016)

  • An efficient method was established for isolation of bifidobacteria from fecal samples of breast-fed infants. The method was based on the combination of Hungate technique applied on anoxic semi-liquid agar tubes, instead of double layer agar plates. Four growth media including BFM, BIM25, MRS and 385 were compared for the isolation efficiency on the basis of Hungate technique. Thus, among 30 isolates obtained from fecal samples of 14 breast fed infants of different ages under 1 year only eight bifidobacteria-like isolates were selected based on cell morphology and fermentation motif. It is revealed that Hungate technique with the use of anaerobic MRS and BFM media was more efficient f...

  • 96.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Bui, Van Loat (2009)

  • The paper resented the results of assessing internal dose for 131I by the direct method for Vietnamese objects that was issued in the Intercomparison Program of IAEA. The results on experimental measurements, caculating intake (I) or 131I to thyroid by the specializing system for measuring thyroid activity, and committed effective dose E(50) using the specializing code of LUDEP 2.0 were shown that the results carrying out at the Nuclear Research Institute were goof and were in accordance with the those of the authors in other laboratories in the world.

  • 117.pdf.jpg
  • 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 n...

  • 122.pdf.jpg
  • Article


  • Authors: Khong, Cat Cuong; Trinh, Duc Thien; Pham, Thu Nga; Nguyen, Van Minh; Nguyen, Van Hung (2009)

  • In this article, we report on the preparation of CdSe quantum dots (QDs) by sol-gel method and their optical properties. The average size of QDs is also estimated by using various ways, such as the Scherer’s formula. The Effros-Brus-Kayanum a's theoretical expression, TEM etc. The TEM images of samples show that the mean sizes of QDs are 4 nm. The mean sizes of QDs are smaller than that of other methods and arranging from 2 to 3.6 nm.

  • 132.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Tran, Trung Dung; Nguyen, Cong Toan (2006)

  • A new procedure for description and calculation of th EXAFS (Extended X-ray Absorption Fine Structure) cumulants for fee crystals containing an abitrary number n of dopant atoms have been developed. Analytical expressions for the l 8t, 2nd and 3rd cumulants have been derived.They depend on the number of dopant atoms and approach those derived by anharmonic correlated Einstein model, if all dopant atoms are taken out or replacing all the host atoms. Numerical results for Cu doped by Ni atoms based on the Morse potential show significant dependence of thermodynamic parameters of the substance on the number of dopant atoms and a reasonable agreement with experiment.

  • 209.pdf.jpg
  • Article


  • Authors: Nguyen, Van Hung; Tran, Trung Dung; Nguyen, Cong Toan (2004)

  • A new procedure for description and calculation of the interaction potential and force constants for fee crystals containing an arbitrary number n of impurity atoms have been developed. Analytical expressions for the effective atomic interaction potential, the single-bond and effective spring constants have been derived. They depend on the number of the impurity atoms and approach those derived by using anharmonic correlated Einstein model, if all the impurity atoms are taken out or they replace all the host atoms. Numerical results for Ni doped by Cu atoms show significant changes of the interact on potential and spring constants of the substance if the number of impurity ato...