Nguyen Quang Minh | Hanoi University (original) (raw)

Papers by Nguyen Quang Minh

Research paper thumbnail of Release of potassium accompanying the dissolution of rice straw phytolith

Chemosphere, 2015

In rice, Si assimilated from the soil solution is deposited in inter- and intracellular spaces th... more In rice, Si assimilated from the soil solution is deposited in inter- and intracellular spaces throughout the leaf and stems to form silicified structures (so-called phytoliths). Because K is also present in significant concentrations in rice stems and leaves, the question arises if K is immobilized in the mineralized silica during the precipitation of Si. This work determined whether desilification of the phytolith is a factor regulating K release by implementing batch experiments. Solubility of Si and K of the rice straw heated at different temperatures were examined to identify effect of pretreatment. Analyses of phytoliths using SEM-EDX and X-ray tomographic microscopy in conjunction with the results from batch experiments revealed that K might co-exist with occluded organic matter inside the phytolith structure. In the kinetic experiments, corresponding increases of K and Si concentrations in the supernatants were observed which suggested that desilification of the phytolith is a main factor regulating K release. The extent of heat pretreatment of the rice straw is of significant importance with respect to dissolution of the phytolith by affecting organic removal and surface modification. At temperatures lower than 600 °C, corresponding increases of the soluble Si and K with heating temperature have been obviously observed. In contrast, the solubility of Si and K gradually decreased at temperatures above 600 °C. This work provides insights into factors that control release of K and Si from phytolith and a practical recommendation for practices of burning rice straw that may maximize subsequent release of Si and K for crops.

Research paper thumbnail of Design and Fabrication of a Miniaturized Three-Degree-of-Freedom Piezoresistive Acceleration Sensor Based on MEMS Technology Using Deep Reactive Ion Etching

Springer Proceedings in Physics, 2009

This paper presents the design and the fabrication of a miniaturized three-degree-of-freedom piez... more This paper presents the design and the fabrication of a miniaturized three-degree-of-freedom piezoresistive acceleration sensor based on MEMS technology using deep reactive ion etching. Finite element method (FEM) using the ANSYS program has been applied to study the mechanical and electrical behavior of the device. The fabricated sensor with the dimension 1 × 1 × 0.45 mm3 can detect simultaneously three components of the linear acceleration at the frequency bandwidth 100 Hz.

Research paper thumbnail of Using Rich Linguistic and Contextual Information for Tree-Based Statistical Machine Translation

2011 International Conference on Asian Language Processing, 2011

This paper presents an approach to select appropriate translation rules to improve phrase-reorder... more This paper presents an approach to select appropriate translation rules to improve phrase-reordering of tree-based statistical machine translation. We propose new features with rich linguistic and contextual information. We give a new algorithm to extract features, use maximum entropy to combine rich linguistic and contextual information and integrate these features into the tree-based SMT model (Moses-chart). We obtain substantial improvements in performance for tree-based translation from Vietnamese to English.

Research paper thumbnail of Vietnamese Noun Phrase Chunking Based on Conditional Random Fields

2009 International Conference on Knowledge and Systems Engineering, 2009

... International Conference on Machine Learning, 2000 [5] Andrew McCallum, “Efficiently Inducing... more ... International Conference on Machine Learning, 2000 [5] Andrew McCallum, “Efficiently Inducing Features of Conditional Random Fields”, Conference on Uncertainty in Artificial Intelligence (UAI), 2003 [6] Akshar Bharathi, Prashanth R.Mannem, “Introduction to the Shallow ...

Research paper thumbnail of Quantum and transport lifetimes due to roughness-induced scattering of a two-dimensional electron gas in wurtzite group-III-nitride heterostructures

Physical Review B, 2006

... Nhat Quang Center for Theoretical Physics, Vietnamese Academy of Science and Technology, PO B... more ... Nhat Quang Center for Theoretical Physics, Vietnamese Academy of Science and Technology, PO Box 429, Boho, Hanoi 10000, Vietnam Nguyen Huyen Tung, Vu Ngoc Tuoc, and NguyenViet Minh Institute of Engineering Physics, Hanoi University of Technology, 1 Dai Co Viet ...

Research paper thumbnail of Roughness-induced mechanisms for electron scattering in wurtzite group-III-nitride heterostructures

Physical Review B, 2005

We present a theory of the low-temperature mobility of the two-dimensional electron gas ͑2DEG͒ in... more We present a theory of the low-temperature mobility of the two-dimensional electron gas ͑2DEG͒ in wurtzite group-III-nitride heterostructures, e.g., AlGaN/ GaN, taking adequate account of the roughness-induced scattering mechanisms and the effect due to sheet polarization charges. The squeeze of the electron distribution in the quantum well by positive piezoelectric and spontaneous polarization-induced charges on the interface is calculated in an analytic form. Thus, we obtained simple expressions describing the squeeze-related enhancement of the 2DEG screening and the unscreened potentials for different scattering sources. Altogether, their screened potentials may be strongly enhanced, so that the 2DEG mobility may be remarkably reduced by sheet polarization charges. Moreover, we proved that the roughness-induced piezoelectric charges and the roughnessinduced deformation potential exhibit new important scattering mechanisms governing the 2DEG transport in wurtzite III-nitride heterostructures. The partial 2DEG mobilities limited by them may be of the order of or less than 10 3 cm 2 / V s. Our theory turns out to be successful in the quantitative explanation of recent experimental data about the high-density 2DEG mobility, e.g., its nonmonotonic dependence on carrier density and its enhancement in the double heterostructure, which have not been understood starting merely from the conventional scattering mechanisms.

Research paper thumbnail of Roughness-induced piezoelectric charges in wurtzite group-III-nitride heterostructures

Physical Review B, 2005

We present a theoretical study of the disorder effect due to interface roughness on piezoelectric... more We present a theoretical study of the disorder effect due to interface roughness on piezoelectricity in wurtzite group-III-nitride heterostructures, eg, AlGaN∕GaN . We have proved that interface roughness gives rise to random nonuniform fluctuations in the piezoelectric polarization. ...

Research paper thumbnail of Flutter responses in long span bridges with wind induced displacement by the mode tracing method

Journal of Wind Engineering and Industrial Aerodynamics, 1998

The problem of flutter prediction for the complex 3D, finite element model of a long span bridge ... more The problem of flutter prediction for the complex 3D, finite element model of a long span bridge has been addressed. Based on a reasonable assumption that the vibration mode does not change abruptly for a gradual increase in the wind speed, a numerical, mode-iteration scheme is proposed. The method is like tracing the system complex mode when the mean wind speed increases; therefore could be used to describe the dynamic behavior before flutter as well. By iteration in function of the mean wind, its effect and the change in the structure configuration and stress can be easily incorporated into the calculation. The final result is thus closer to the reality. The flutter behavior and flutter modes from the mode tracing method can also be used for the buffeting analysis. Once the complex modes and complex modal forces are known, the modal equation can be formed and a time history integration can be carried out to determine the buffeting responses. A numerical example based on the full model bridge has been conducted and compared with the data of experiments on 3D model in a wind tunnel. The results obtained have shown that the method is accurate and computationally efficient among the full model analysis methods.

Research paper thumbnail of Improvement of electrical property for Pb(Zr 0.53 Ti 0.47 )O 3 ferroelectric thin film deposited by sol-gel method on SRO electrode

Journal of Physics: Conference Series, 2009

Pb(Zr,Ti)O 3 thin films with Zr/Ti ratio of 53:47 were deposited on SRO/YSZ/Si(100) and Pt/Ti/SiO... more Pb(Zr,Ti)O 3 thin films with Zr/Ti ratio of 53:47 were deposited on SRO/YSZ/Si(100) and Pt/Ti/SiO 2 /Si(100) substrates using the sol-gel method. The thermal process of the PZT thin films included treating two-step pyrolysis, at 300 o C for 30 minutes and 400 o C for 10 minutes, and annealing crystallization, at 600 o C for 10 minutes in air ambient. The remnant polarization and the coercive field of the PZT/SRO/YSZ/Si were 28 μC/cm 2 and 65 kV/cm 2 , and those of the PZT/Pt/Ti/SiO 2 /Si were 12 μC/cm 2 and 79 kV/cm 2 . This indicates that the use of the metallic SRO-electrodes significantly improves electrical property of PZT piezoelectric thin film as compared with a metal-electrode Pt.

Research paper thumbnail of Path Integral Quantization of Self Interacting Scalar Field with Higher Derivatives

Arxiv preprint arXiv:0709.4522, 2007

Abstract: Scalar field systems containing higher derivatives are studied and quantized by Hamilto... more Abstract: Scalar field systems containing higher derivatives are studied and quantized by Hamiltonian path integral formalism. A new point to previous quantization methods is that field functions and their derivatives with time are considered as independent canonical ...

Research paper thumbnail of Pro-poor intervention strategies in irrigated agriculture in Asia: issues, lessons, options and guidelines

Irrigation and Drainage, 2007

... Agriculture Faisalabad), Mr Salman Sarwar (Development Officer, INPIM), Mr Zeeshan Naseer (De... more ... Agriculture Faisalabad), Mr Salman Sarwar (Development Officer, INPIM), Mr Zeeshan Naseer (Development Officer, INPIM), Mr Qasim Manzoor (Development Officer, INPIM), Mr Irfan Baig (INPIM Fellow) and Mr M. Arif Raza (INPIM Fellow) for their assistance in editorial and ...

Research paper thumbnail of Effect of anions on dispersion of a kaolinitic soil clay: A combined study of dynamic light scattering and test tube experiments

Geoderma, 2013

Dispersion is an important issue for clay leaching in soils. In this study, effects of various an... more Dispersion is an important issue for clay leaching in soils. In this study, effects of various anions (Cl − , SO 4 2− , acetate, oxalate and citrate) on dispersion of a kaolinitic soil clay were determined at different pH values and ionic strengths by dynamic light scattering and test tube experiments. Adsorption of anions on clay samples was characterized by the zeta potential (ζ) in a pH range of 2 to 11. At a pH range between 2 and 6, the effects of different anions on decreasing ζ were obvious and followed the order oxalate N citrate N SO 4 2− N Cl − N acetate, while fluctuated changes in ζ were observed at pH N 6. Based on a comparison of hydrodynamic radii (r h ) obtained from dynamic light scattering and of transmission of 50% (T 50 values) from the test tube experiments, the ability of anions to facilitate the dispersion of the clay fraction followed the sequence of oxalate N citrate N acetate N SO 4 2− N Cl − . It implies that adsorption of anions on positively charged edge sites of kaolinite resulting in a decrease in ζ is a key factor for dispersion of the clay fraction. Also, the results suggested that the dynamic light scattering can be used in combination with the test tube experiments in order to evaluate the effect of anions on dispersion at broader ranges of pH, ionic strength and clay concentration.

Research paper thumbnail of A facile thermal evaporation route for large-area synthesis of tin oxide nanowires: Characterizations and their use for liquid petroleum gas sensor

Current Applied Physics, 2010

In this paper, a very simple procedure was presented for the reproducible synthesis of large-area... more In this paper, a very simple procedure was presented for the reproducible synthesis of large-area SnO2 nanowires (NWs) on a silicon substrate by evaporating Sn powders at temperatures of 700, 750, and 800 °C. As-obtained SnO2 NWs were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy. They revealed that the morphology of the NWs is affected by growth temperature and the SnO2 NWs are singlecrystalline tetragonal. The band gap of the NWs is in the range of 4.2-4.3 eV as determined from UV/visible absorption. The NWs show stable photoluminescence with an emission peak centered at around 620 nm at room-temperature. The sensors fabricated from the SnO2 NWs synthesized at 700 °C exhibited good response to LPG (liquefied petroleum gas) at an operating temperature of 400 °C.

Research paper thumbnail of Syntheses, Crystal Structures, and Magnetic Properties of a Stable Aminoxyl Radical and Its Copper(II) Complex

Research paper thumbnail of On Castelnuovo-Mumford regularity of products of monomial ideals

Let R = k[x1,x2,... ,xu] be a polynomial ring over a field k and I ⊂ R a homogeneous ideal. The C... more Let R = k[x1,x2,... ,xu] be a polynomial ring over a field k and I ⊂ R a homogeneous ideal. The Castelnuovo-Mumford regularity of I governs the degrees appearing in a minimal graded free resolution of I. Conca and Herzog ([CH]) raised the following question: Whether it is true that

Research paper thumbnail of On the regularity of products and intersections of complete intersections

Proceedings of the American …, 2007

This paper proves the formulae reg(IJ) ≤ reg(I) + reg(J), reg(I ∩ J) ≤ reg(I) + reg(J) for arbitr... more This paper proves the formulae reg(IJ) ≤ reg(I) + reg(J), reg(I ∩ J) ≤ reg(I) + reg(J) for arbitrary monomial complete intersections I and J, and provides examples showing that these inequalities do not hold for general complete intersections.

Research paper thumbnail of Cohen-Macaulayness of monomial ideals and symbolic powers of Stanley-Reisner ideals

We present criteria for the Cohen-Macaulayness of a monomial ideal in terms of its primary decomp... more We present criteria for the Cohen-Macaulayness of a monomial ideal in terms of its primary decomposition. These criteria allow us to use tools of graph theory and of linear programming to study the Cohen-Macaulayness of monomial ideals which are intersections of prime ideal powers. We can characterize the Cohen-Macaulayness of the second symbolic power or of all symbolic powers of a Stanley-Reisner ideal in terms of the simplicial complex. These characterizations show that the simplicial complex must be very compact if some symbolic power is Cohen-Macaulay. In particular, all symbolic powers are Cohen-Macaulay if and only if the simplicial complex is a matroid complex. We also prove that the Cohen-Macaulayness can pass from a symbolic power to another symbolic powers in different ways.

Research paper thumbnail of Periodic Solutions of Linear Differential Equations (Qualitative theory of functional equations and its application to mathematical science)

Title Periodic Solutions of Linear Differential Equations (Qualitative theory of functional equat... more Title Periodic Solutions of Linear Differential Equations (Qualitative theory of functional equations and its application to mathematical science) ... Author(s) Naito, Toshiki; Shin, Jong Son; Minh, Nguyen Van ... 電気通信大学 内藤敏機 (Toshiki Naito) 朝鮮大学校 申 正善 (Jong ...

Research paper thumbnail of A topological classification of differential equations with impulse effect

Tamkang Journal of Mathematics

ABSTRACT

Research paper thumbnail of Application of Raman Scattering to Investigate the Superconductors

Infrared absorption, light scattering and neutron scattering are most commonly used techniques fo... more Infrared absorption, light scattering and neutron scattering are most commonly used techniques for investigating low-energy elementary excitations in solids, in particular phonons. A detailed knowledge of the symmetry and atomic eigenvectors associated with each vibrational mode provides important information concerning the structure and physical properties of a material. Given such information one can learn about other excitations in the system

Research paper thumbnail of Release of potassium accompanying the dissolution of rice straw phytolith

Chemosphere, 2015

In rice, Si assimilated from the soil solution is deposited in inter- and intracellular spaces th... more In rice, Si assimilated from the soil solution is deposited in inter- and intracellular spaces throughout the leaf and stems to form silicified structures (so-called phytoliths). Because K is also present in significant concentrations in rice stems and leaves, the question arises if K is immobilized in the mineralized silica during the precipitation of Si. This work determined whether desilification of the phytolith is a factor regulating K release by implementing batch experiments. Solubility of Si and K of the rice straw heated at different temperatures were examined to identify effect of pretreatment. Analyses of phytoliths using SEM-EDX and X-ray tomographic microscopy in conjunction with the results from batch experiments revealed that K might co-exist with occluded organic matter inside the phytolith structure. In the kinetic experiments, corresponding increases of K and Si concentrations in the supernatants were observed which suggested that desilification of the phytolith is a main factor regulating K release. The extent of heat pretreatment of the rice straw is of significant importance with respect to dissolution of the phytolith by affecting organic removal and surface modification. At temperatures lower than 600 °C, corresponding increases of the soluble Si and K with heating temperature have been obviously observed. In contrast, the solubility of Si and K gradually decreased at temperatures above 600 °C. This work provides insights into factors that control release of K and Si from phytolith and a practical recommendation for practices of burning rice straw that may maximize subsequent release of Si and K for crops.

Research paper thumbnail of Design and Fabrication of a Miniaturized Three-Degree-of-Freedom Piezoresistive Acceleration Sensor Based on MEMS Technology Using Deep Reactive Ion Etching

Springer Proceedings in Physics, 2009

This paper presents the design and the fabrication of a miniaturized three-degree-of-freedom piez... more This paper presents the design and the fabrication of a miniaturized three-degree-of-freedom piezoresistive acceleration sensor based on MEMS technology using deep reactive ion etching. Finite element method (FEM) using the ANSYS program has been applied to study the mechanical and electrical behavior of the device. The fabricated sensor with the dimension 1 × 1 × 0.45 mm3 can detect simultaneously three components of the linear acceleration at the frequency bandwidth 100 Hz.

Research paper thumbnail of Using Rich Linguistic and Contextual Information for Tree-Based Statistical Machine Translation

2011 International Conference on Asian Language Processing, 2011

This paper presents an approach to select appropriate translation rules to improve phrase-reorder... more This paper presents an approach to select appropriate translation rules to improve phrase-reordering of tree-based statistical machine translation. We propose new features with rich linguistic and contextual information. We give a new algorithm to extract features, use maximum entropy to combine rich linguistic and contextual information and integrate these features into the tree-based SMT model (Moses-chart). We obtain substantial improvements in performance for tree-based translation from Vietnamese to English.

Research paper thumbnail of Vietnamese Noun Phrase Chunking Based on Conditional Random Fields

2009 International Conference on Knowledge and Systems Engineering, 2009

... International Conference on Machine Learning, 2000 [5] Andrew McCallum, “Efficiently Inducing... more ... International Conference on Machine Learning, 2000 [5] Andrew McCallum, “Efficiently Inducing Features of Conditional Random Fields”, Conference on Uncertainty in Artificial Intelligence (UAI), 2003 [6] Akshar Bharathi, Prashanth R.Mannem, “Introduction to the Shallow ...

Research paper thumbnail of Quantum and transport lifetimes due to roughness-induced scattering of a two-dimensional electron gas in wurtzite group-III-nitride heterostructures

Physical Review B, 2006

... Nhat Quang Center for Theoretical Physics, Vietnamese Academy of Science and Technology, PO B... more ... Nhat Quang Center for Theoretical Physics, Vietnamese Academy of Science and Technology, PO Box 429, Boho, Hanoi 10000, Vietnam Nguyen Huyen Tung, Vu Ngoc Tuoc, and NguyenViet Minh Institute of Engineering Physics, Hanoi University of Technology, 1 Dai Co Viet ...

Research paper thumbnail of Roughness-induced mechanisms for electron scattering in wurtzite group-III-nitride heterostructures

Physical Review B, 2005

We present a theory of the low-temperature mobility of the two-dimensional electron gas ͑2DEG͒ in... more We present a theory of the low-temperature mobility of the two-dimensional electron gas ͑2DEG͒ in wurtzite group-III-nitride heterostructures, e.g., AlGaN/ GaN, taking adequate account of the roughness-induced scattering mechanisms and the effect due to sheet polarization charges. The squeeze of the electron distribution in the quantum well by positive piezoelectric and spontaneous polarization-induced charges on the interface is calculated in an analytic form. Thus, we obtained simple expressions describing the squeeze-related enhancement of the 2DEG screening and the unscreened potentials for different scattering sources. Altogether, their screened potentials may be strongly enhanced, so that the 2DEG mobility may be remarkably reduced by sheet polarization charges. Moreover, we proved that the roughness-induced piezoelectric charges and the roughnessinduced deformation potential exhibit new important scattering mechanisms governing the 2DEG transport in wurtzite III-nitride heterostructures. The partial 2DEG mobilities limited by them may be of the order of or less than 10 3 cm 2 / V s. Our theory turns out to be successful in the quantitative explanation of recent experimental data about the high-density 2DEG mobility, e.g., its nonmonotonic dependence on carrier density and its enhancement in the double heterostructure, which have not been understood starting merely from the conventional scattering mechanisms.

Research paper thumbnail of Roughness-induced piezoelectric charges in wurtzite group-III-nitride heterostructures

Physical Review B, 2005

We present a theoretical study of the disorder effect due to interface roughness on piezoelectric... more We present a theoretical study of the disorder effect due to interface roughness on piezoelectricity in wurtzite group-III-nitride heterostructures, eg, AlGaN∕GaN . We have proved that interface roughness gives rise to random nonuniform fluctuations in the piezoelectric polarization. ...

Research paper thumbnail of Flutter responses in long span bridges with wind induced displacement by the mode tracing method

Journal of Wind Engineering and Industrial Aerodynamics, 1998

The problem of flutter prediction for the complex 3D, finite element model of a long span bridge ... more The problem of flutter prediction for the complex 3D, finite element model of a long span bridge has been addressed. Based on a reasonable assumption that the vibration mode does not change abruptly for a gradual increase in the wind speed, a numerical, mode-iteration scheme is proposed. The method is like tracing the system complex mode when the mean wind speed increases; therefore could be used to describe the dynamic behavior before flutter as well. By iteration in function of the mean wind, its effect and the change in the structure configuration and stress can be easily incorporated into the calculation. The final result is thus closer to the reality. The flutter behavior and flutter modes from the mode tracing method can also be used for the buffeting analysis. Once the complex modes and complex modal forces are known, the modal equation can be formed and a time history integration can be carried out to determine the buffeting responses. A numerical example based on the full model bridge has been conducted and compared with the data of experiments on 3D model in a wind tunnel. The results obtained have shown that the method is accurate and computationally efficient among the full model analysis methods.

Research paper thumbnail of Improvement of electrical property for Pb(Zr 0.53 Ti 0.47 )O 3 ferroelectric thin film deposited by sol-gel method on SRO electrode

Journal of Physics: Conference Series, 2009

Pb(Zr,Ti)O 3 thin films with Zr/Ti ratio of 53:47 were deposited on SRO/YSZ/Si(100) and Pt/Ti/SiO... more Pb(Zr,Ti)O 3 thin films with Zr/Ti ratio of 53:47 were deposited on SRO/YSZ/Si(100) and Pt/Ti/SiO 2 /Si(100) substrates using the sol-gel method. The thermal process of the PZT thin films included treating two-step pyrolysis, at 300 o C for 30 minutes and 400 o C for 10 minutes, and annealing crystallization, at 600 o C for 10 minutes in air ambient. The remnant polarization and the coercive field of the PZT/SRO/YSZ/Si were 28 μC/cm 2 and 65 kV/cm 2 , and those of the PZT/Pt/Ti/SiO 2 /Si were 12 μC/cm 2 and 79 kV/cm 2 . This indicates that the use of the metallic SRO-electrodes significantly improves electrical property of PZT piezoelectric thin film as compared with a metal-electrode Pt.

Research paper thumbnail of Path Integral Quantization of Self Interacting Scalar Field with Higher Derivatives

Arxiv preprint arXiv:0709.4522, 2007

Abstract: Scalar field systems containing higher derivatives are studied and quantized by Hamilto... more Abstract: Scalar field systems containing higher derivatives are studied and quantized by Hamiltonian path integral formalism. A new point to previous quantization methods is that field functions and their derivatives with time are considered as independent canonical ...

Research paper thumbnail of Pro-poor intervention strategies in irrigated agriculture in Asia: issues, lessons, options and guidelines

Irrigation and Drainage, 2007

... Agriculture Faisalabad), Mr Salman Sarwar (Development Officer, INPIM), Mr Zeeshan Naseer (De... more ... Agriculture Faisalabad), Mr Salman Sarwar (Development Officer, INPIM), Mr Zeeshan Naseer (Development Officer, INPIM), Mr Qasim Manzoor (Development Officer, INPIM), Mr Irfan Baig (INPIM Fellow) and Mr M. Arif Raza (INPIM Fellow) for their assistance in editorial and ...

Research paper thumbnail of Effect of anions on dispersion of a kaolinitic soil clay: A combined study of dynamic light scattering and test tube experiments

Geoderma, 2013

Dispersion is an important issue for clay leaching in soils. In this study, effects of various an... more Dispersion is an important issue for clay leaching in soils. In this study, effects of various anions (Cl − , SO 4 2− , acetate, oxalate and citrate) on dispersion of a kaolinitic soil clay were determined at different pH values and ionic strengths by dynamic light scattering and test tube experiments. Adsorption of anions on clay samples was characterized by the zeta potential (ζ) in a pH range of 2 to 11. At a pH range between 2 and 6, the effects of different anions on decreasing ζ were obvious and followed the order oxalate N citrate N SO 4 2− N Cl − N acetate, while fluctuated changes in ζ were observed at pH N 6. Based on a comparison of hydrodynamic radii (r h ) obtained from dynamic light scattering and of transmission of 50% (T 50 values) from the test tube experiments, the ability of anions to facilitate the dispersion of the clay fraction followed the sequence of oxalate N citrate N acetate N SO 4 2− N Cl − . It implies that adsorption of anions on positively charged edge sites of kaolinite resulting in a decrease in ζ is a key factor for dispersion of the clay fraction. Also, the results suggested that the dynamic light scattering can be used in combination with the test tube experiments in order to evaluate the effect of anions on dispersion at broader ranges of pH, ionic strength and clay concentration.

Research paper thumbnail of A facile thermal evaporation route for large-area synthesis of tin oxide nanowires: Characterizations and their use for liquid petroleum gas sensor

Current Applied Physics, 2010

In this paper, a very simple procedure was presented for the reproducible synthesis of large-area... more In this paper, a very simple procedure was presented for the reproducible synthesis of large-area SnO2 nanowires (NWs) on a silicon substrate by evaporating Sn powders at temperatures of 700, 750, and 800 °C. As-obtained SnO2 NWs were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy. They revealed that the morphology of the NWs is affected by growth temperature and the SnO2 NWs are singlecrystalline tetragonal. The band gap of the NWs is in the range of 4.2-4.3 eV as determined from UV/visible absorption. The NWs show stable photoluminescence with an emission peak centered at around 620 nm at room-temperature. The sensors fabricated from the SnO2 NWs synthesized at 700 °C exhibited good response to LPG (liquefied petroleum gas) at an operating temperature of 400 °C.

Research paper thumbnail of Syntheses, Crystal Structures, and Magnetic Properties of a Stable Aminoxyl Radical and Its Copper(II) Complex

Research paper thumbnail of On Castelnuovo-Mumford regularity of products of monomial ideals

Let R = k[x1,x2,... ,xu] be a polynomial ring over a field k and I ⊂ R a homogeneous ideal. The C... more Let R = k[x1,x2,... ,xu] be a polynomial ring over a field k and I ⊂ R a homogeneous ideal. The Castelnuovo-Mumford regularity of I governs the degrees appearing in a minimal graded free resolution of I. Conca and Herzog ([CH]) raised the following question: Whether it is true that

Research paper thumbnail of On the regularity of products and intersections of complete intersections

Proceedings of the American …, 2007

This paper proves the formulae reg(IJ) ≤ reg(I) + reg(J), reg(I ∩ J) ≤ reg(I) + reg(J) for arbitr... more This paper proves the formulae reg(IJ) ≤ reg(I) + reg(J), reg(I ∩ J) ≤ reg(I) + reg(J) for arbitrary monomial complete intersections I and J, and provides examples showing that these inequalities do not hold for general complete intersections.

Research paper thumbnail of Cohen-Macaulayness of monomial ideals and symbolic powers of Stanley-Reisner ideals

We present criteria for the Cohen-Macaulayness of a monomial ideal in terms of its primary decomp... more We present criteria for the Cohen-Macaulayness of a monomial ideal in terms of its primary decomposition. These criteria allow us to use tools of graph theory and of linear programming to study the Cohen-Macaulayness of monomial ideals which are intersections of prime ideal powers. We can characterize the Cohen-Macaulayness of the second symbolic power or of all symbolic powers of a Stanley-Reisner ideal in terms of the simplicial complex. These characterizations show that the simplicial complex must be very compact if some symbolic power is Cohen-Macaulay. In particular, all symbolic powers are Cohen-Macaulay if and only if the simplicial complex is a matroid complex. We also prove that the Cohen-Macaulayness can pass from a symbolic power to another symbolic powers in different ways.

Research paper thumbnail of Periodic Solutions of Linear Differential Equations (Qualitative theory of functional equations and its application to mathematical science)

Title Periodic Solutions of Linear Differential Equations (Qualitative theory of functional equat... more Title Periodic Solutions of Linear Differential Equations (Qualitative theory of functional equations and its application to mathematical science) ... Author(s) Naito, Toshiki; Shin, Jong Son; Minh, Nguyen Van ... 電気通信大学 内藤敏機 (Toshiki Naito) 朝鮮大学校 申 正善 (Jong ...

Research paper thumbnail of A topological classification of differential equations with impulse effect

Tamkang Journal of Mathematics

ABSTRACT

Research paper thumbnail of Application of Raman Scattering to Investigate the Superconductors

Infrared absorption, light scattering and neutron scattering are most commonly used techniques fo... more Infrared absorption, light scattering and neutron scattering are most commonly used techniques for investigating low-energy elementary excitations in solids, in particular phonons. A detailed knowledge of the symmetry and atomic eigenvectors associated with each vibrational mode provides important information concerning the structure and physical properties of a material. Given such information one can learn about other excitations in the system