ABSTRACT The strain dependence of the solution energy of substitutional species is derived by exp... more ABSTRACT The strain dependence of the solution energy of substitutional species is derived by expanding the binary alloy energy with respect to concentration and strain to the second order. Within the approximation of small strain and concentration inhomogeneities, the energy change is found to be proportional to the solute-induced stress, and the strain dependence of the solute energy is equivalent to that from the misfit model for solute atoms. However, the solute induced stress is easily calculated from first principles, and it is computed for Ag, Cu, Fe, Li, Mg, Mn, Si, and Zn atoms in aluminum. The results are used to estimate the solute-dislocation interaction energy. The enhancement of the solute concentration near a dislocation core and the role of dislocations on precipitation of these solutes are discussed.
2012 9th International Conference on Electrical Engineering/Electronics, Computer, Telecommunications and Information Technology, 2012
ABSTRACT This paper introduces a new approach for visualizing multidimentional weather-direction-... more ABSTRACT This paper introduces a new approach for visualizing multidimentional weather-direction-related time-series data sets called “3D Spring Model”. Spring Model is designed to visualize pattern behind large time-series weather data set and to clearify seasonal structure in the data. In addition, it supports visibility of seasonal shift and wind direction anomaly by direct comparison betweem successive spring cycles. The visualization contained three data types: (1) Weather parameter (such as windrun, temperature or rainfall etc.), (2) Wind directions and (3) time. We mapped the color to the model in such the way that it comply with human perception using color gradient. Level-Of-Detail scheme is applied and adjustable resulting different pattern time focus for users. Spring Model is highly self-contained for accumulative long term data. It is interactive, flexible and user-friendly. Spring Model is very well-suited to high computing power visualization environment. At the end of the paper, the observation of weather pattern in Nakhon Si Thammarat, Thailand using Spring Model was proposed as the case study to present the model vast applications.
ABSTRACT Self-assembled islands are spontaneously formed during the heteroepitaxial growth of InA... more ABSTRACT Self-assembled islands are spontaneously formed during the heteroepitaxial growth of InAs on GaAs substrate. The island formation creates strain fields in the substrate and this leads to elastic interaction between the islands. We calculate the strain energy of the array of InAs islands on the GaAs substrate by the finite element method, and extract the elastic interaction between the islands from the variation of the energy with the distance between the islands. The interaction decays with the third power of the inter-island distance, in agreement with our previous work. The effect of the interaction on the correlation of the island positions is examined by comparing the coefficient of the interaction with the phase transition criteria of the two-dimensional dipole system. When the island size is large enough, depending on the island density, an array of islands can be in either a liquid phase where the islands are randomly distributed or in a solid phase where the islands form a two dimensional lattice. Only the liquid phase exists when the island size is small.
ABSTRACT The dependence of the solute atom energy on the homogeneous strain is derived by expandi... more ABSTRACT The dependence of the solute atom energy on the homogeneous strain is derived by expanding the energy of the binary alloy to the second order in the solute concentration and the homogeneous strain components. The energy change is found to be proportional to the solute induced stress. An ab-initio method is then applied to calculate the solute induced stress for Cu, Fe, Li, Mg, Mn, Si, and Zn solute atoms in aluminum.
ABSTRACT The formation enthalpy of the InGa defect in GaAs was calculated ab initio by a hybrid m... more ABSTRACT The formation enthalpy of the InGa defect in GaAs was calculated ab initio by a hybrid method consisting of an atomistic- and a continuum calculation. The atomic relaxation of the lattice near the defect was treated with an atomistic calculation, whereas the long-ranged elastic strain energy was obtained from a linear elastic continuum calculation. The solubility of InAs in GaAs at room temperature and the maximum temperature of the miscibility gap in the solid solution phase were determined from the defect formation enthalpy. The results are in good agreement with a thermodynamic assessment. The effect of lattice coherency on the c/a ratio of epitaxial InAs monolayers grown on (100) GaAs substrates is determined. The stability of such InAs layers with respect to the Ga-rich InxGa1−xAs solid solution is predicted.
ABSTRACT Proton transfer is a governing factor in the proton exchange efficiency in membrane fuel... more ABSTRACT Proton transfer is a governing factor in the proton exchange efficiency in membrane fuel cells (PEMFCs), which are an alternative environmentally friendly resource. To develop the capacity of the PEMFC system, anhydrous membranes containing imidazole groups have garnered much interest. In this research, the relationship between the hydrogen bond networks, including the consequent packing structure, and the proton conductivity of water and imidazole (Im) systems have been systematically studied. The effect of external electrostatic perturbation was investigated in (H2O)H+⋯H2O, (Im)H+⋯Im, bulk water, and imidazole superlattice systems. In all of these cases, the application of an electric field in a direction opposite to that of the overall system dipole significantly reduces the activation barrier for proton transport. In isolated systems, (H2O)H+⋯H2O and (Im)H+⋯Im, the preferred orientation angle between the neighbouring molecules was 90°. From density functional molecular dynamics simulations of the bulk system, the proton diffusion coefficient was found to increase under the perturbation by the applied electric fields in range of 1.29 × 107 to 3.86 × 107 V cm−1 (0.0025–0.0075 a.u.) for both water and imidazole. To trace the efficient proton transfer, the proton movement trajectory was explicitly analysed in detail. Interestingly, a tilted proton hopping direction was found for imidazole crystal.
Ab initio calculation based on density functional theory was performed for studying high-pressure... more Ab initio calculation based on density functional theory was performed for studying high-pressure effects on the electronic properties and photoabsorption of Ga(1-x)Mn(x)As. Mn atom was substituted into the varied GaAs supercells, which observed the Mn concentrations at 3.70%, 8.33% and 12.50%. In zinc blende phase of Ga(1-x)Mn(x)As, we found that the effects of Mn on GaAs in the pressure range 0–10 GPa are the reducing of bandgap, generating of impurity peak and increasing of photoabsorption coefficient. The impurity peaks in Ga(1-x)Mn(x)As decrease under pressure increasing because the carriers were excited to conduction band by the effect of bond lengths reducing. The tendency of absorption coefficient of Ga(1-x)Mn(x)As in range of light-wavelength depends on size of impurity peak.
Imagery of ecological systems can be used to observe organisms, to observe rare events and to doc... more Imagery of ecological systems can be used to observe organisms, to observe rare events and to document long-term changes in ecological systems. Here we describe a system used for archiving and sharing imagery with ecological researchers Thailand, and present some examples of their use. The Coral Virtual System monitors a coral ecosystem at the Racha Island, Phuket, Thailand. The Coral
Ab initio calculations were performed for investigating the high pressure phases of GaAs upto 200... more Ab initio calculations were performed for investigating the high pressure phases of GaAs upto 200GPa. By comparing the minimum free energies of structures, we found the thermodynamically stable phases of GaAs under pressure beyond GaAs-III (Imm2) with space groups Pmma and P4/nmm at the pressure range of 88–146 GPa and 146-200GPa, respectively. For discussing the difference results of GaAs IV and V in previous studies, we found that Pmma and P4/nmm are the lower symmetric phases of P6/mmm and CsCl-like, respectively. For analyzing the Pmma-P4/nmm phase transition, we observed the approximated path and found that the barrier of transformation from Pmma to P4/nmm in direction [110] is 0.035 eV. The graph of density of states shows no energy gap in stable phases at 130 and 160 GPa, indicating that Pmma and P4/nmm are the metallic phases. The contour plots of the electron density difference show some valence electron sharing in Pmma which is higher than in P4/nmm. Moreover, the results of elastic parameters and modulus ratio suggested that the Pmma phase is a ductile material, while the P4/nmm phase is a brittle due to the increasing of shear modulus.
ABSTRACT Heath information across geographically distributed healthcare centers has been recogniz... more ABSTRACT Heath information across geographically distributed healthcare centers has been recognized as an essential resource that drives an efficient national health-care plan. There is thus a need for the National Health Information System (NHIS) that provides the transparent and secure access to health information from different healthcare centers both on demand and in a time efficient manner. As healthiness is the ultimate goal of people and nation, we believe that the NHIS should be sustainable by taking the healthcare center and information consumer perspectives into account. Several issues in particular must be resolved altogether: (i) the diversity of health information structures among healthcare centers; (ii) the availability of health information sharing from healthcare centers; (iii) the efficient information access to various healthcare centers; and (iv) the privacy and privilege of heath information. To achieve the sustainable NHIS, this paper details our work which is divided into 3 main phases. Essentially, the first phase focuses on the application of metadata standard to enable the interoperability and usability of health information across healthcare centers. The second phase moves forward to make information sharing possible and to provide an efficient information access to a large number of healthcare centers. Finally, in the third phase, the privacy and privilege of health information is promoted with respect to access rights of information consumers.
ABSTRACT This paper presents eInformatorium -- a one-stop and multi-faceted observation data serv... more ABSTRACT This paper presents eInformatorium -- a one-stop and multi-faceted observation data service. In particular, eInformatorium enables users to simply (i) acquire any observation data of interest across geographically distributed repositories via a single point access, and (ii) visualize any observation data of choice in a desirable graphical presentation on demand and in a user-oriented manner. The applicability of eInformatorium is currently evaluated by a few users. The result has shown that eInformatorium enables users to simply acquire the preferable visualized observation data in a time and budget efficient manner. It also leads them to further conduct detailed studies and decisions. Last but not least, beside users, eInformatorium encourages repository owners to register and share their belonging observation data.
The ground state and the lowest singlet excited-state geometries of poly-(9,9-dialkylfluorene-2,7... more The ground state and the lowest singlet excited-state geometries of poly-(9,9-dialkylfluorene-2,7-vinylene) copolymer or PFV and its derivatives (NH2–FV)n, (CN–FV)n, (OMe–FV)n and (OH–FV)n (n=2–5) were investigated based on density functional theory (DFT) and time-dependent DFT using B3LYP functional. The ground state and the lowest singlet excited-state geometries of the oligomers were optimized at the B3LYP/6-31G∗ and TD-B3LYP/SVP levels, respectively. The calculated
We used an ab initio method to calculate the high pressure phases of CuInSe2. By using the experi... more We used an ab initio method to calculate the high pressure phases of CuInSe2. By using the experimentally suggested phases, the enthalpy difference showed that the I-42d structure transforms into Fm-3m at 12 GPa and then into Cmcm at 42 GPa. The volume reductions at each phase transition are 13.9% and 1.9% respectively, compared with 11% and 1% from experiments. By using the sX-LDA functional, we found that the bandgap in the I-42d structure increases at the rate of 39.6 meV/GPa, in fair agreement with photoabsorption experiments. The band gap is closed in the Fm-3m and Cmcm structures. The bond lengths between Cu-Se and In–Se were investigated. We found that the bond lengths can be related to the behavior of the energy gap under high pressure. The path of transformation from Fm-3m to Cmcm was proposed. The energy barrier between the two phases was estimated. The upper bound of the energy barrier is 17 meV which is equivalent to 198 K. This finding can explain the existence of two phases at room temperature reported by experimental study.
ABSTRACT The strain dependence of the solution energy of substitutional species is derived by exp... more ABSTRACT The strain dependence of the solution energy of substitutional species is derived by expanding the binary alloy energy with respect to concentration and strain to the second order. Within the approximation of small strain and concentration inhomogeneities, the energy change is found to be proportional to the solute-induced stress, and the strain dependence of the solute energy is equivalent to that from the misfit model for solute atoms. However, the solute induced stress is easily calculated from first principles, and it is computed for Ag, Cu, Fe, Li, Mg, Mn, Si, and Zn atoms in aluminum. The results are used to estimate the solute-dislocation interaction energy. The enhancement of the solute concentration near a dislocation core and the role of dislocations on precipitation of these solutes are discussed.
2012 9th International Conference on Electrical Engineering/Electronics, Computer, Telecommunications and Information Technology, 2012
ABSTRACT This paper introduces a new approach for visualizing multidimentional weather-direction-... more ABSTRACT This paper introduces a new approach for visualizing multidimentional weather-direction-related time-series data sets called “3D Spring Model”. Spring Model is designed to visualize pattern behind large time-series weather data set and to clearify seasonal structure in the data. In addition, it supports visibility of seasonal shift and wind direction anomaly by direct comparison betweem successive spring cycles. The visualization contained three data types: (1) Weather parameter (such as windrun, temperature or rainfall etc.), (2) Wind directions and (3) time. We mapped the color to the model in such the way that it comply with human perception using color gradient. Level-Of-Detail scheme is applied and adjustable resulting different pattern time focus for users. Spring Model is highly self-contained for accumulative long term data. It is interactive, flexible and user-friendly. Spring Model is very well-suited to high computing power visualization environment. At the end of the paper, the observation of weather pattern in Nakhon Si Thammarat, Thailand using Spring Model was proposed as the case study to present the model vast applications.
ABSTRACT Self-assembled islands are spontaneously formed during the heteroepitaxial growth of InA... more ABSTRACT Self-assembled islands are spontaneously formed during the heteroepitaxial growth of InAs on GaAs substrate. The island formation creates strain fields in the substrate and this leads to elastic interaction between the islands. We calculate the strain energy of the array of InAs islands on the GaAs substrate by the finite element method, and extract the elastic interaction between the islands from the variation of the energy with the distance between the islands. The interaction decays with the third power of the inter-island distance, in agreement with our previous work. The effect of the interaction on the correlation of the island positions is examined by comparing the coefficient of the interaction with the phase transition criteria of the two-dimensional dipole system. When the island size is large enough, depending on the island density, an array of islands can be in either a liquid phase where the islands are randomly distributed or in a solid phase where the islands form a two dimensional lattice. Only the liquid phase exists when the island size is small.
ABSTRACT The dependence of the solute atom energy on the homogeneous strain is derived by expandi... more ABSTRACT The dependence of the solute atom energy on the homogeneous strain is derived by expanding the energy of the binary alloy to the second order in the solute concentration and the homogeneous strain components. The energy change is found to be proportional to the solute induced stress. An ab-initio method is then applied to calculate the solute induced stress for Cu, Fe, Li, Mg, Mn, Si, and Zn solute atoms in aluminum.
ABSTRACT The formation enthalpy of the InGa defect in GaAs was calculated ab initio by a hybrid m... more ABSTRACT The formation enthalpy of the InGa defect in GaAs was calculated ab initio by a hybrid method consisting of an atomistic- and a continuum calculation. The atomic relaxation of the lattice near the defect was treated with an atomistic calculation, whereas the long-ranged elastic strain energy was obtained from a linear elastic continuum calculation. The solubility of InAs in GaAs at room temperature and the maximum temperature of the miscibility gap in the solid solution phase were determined from the defect formation enthalpy. The results are in good agreement with a thermodynamic assessment. The effect of lattice coherency on the c/a ratio of epitaxial InAs monolayers grown on (100) GaAs substrates is determined. The stability of such InAs layers with respect to the Ga-rich InxGa1−xAs solid solution is predicted.
ABSTRACT Proton transfer is a governing factor in the proton exchange efficiency in membrane fuel... more ABSTRACT Proton transfer is a governing factor in the proton exchange efficiency in membrane fuel cells (PEMFCs), which are an alternative environmentally friendly resource. To develop the capacity of the PEMFC system, anhydrous membranes containing imidazole groups have garnered much interest. In this research, the relationship between the hydrogen bond networks, including the consequent packing structure, and the proton conductivity of water and imidazole (Im) systems have been systematically studied. The effect of external electrostatic perturbation was investigated in (H2O)H+⋯H2O, (Im)H+⋯Im, bulk water, and imidazole superlattice systems. In all of these cases, the application of an electric field in a direction opposite to that of the overall system dipole significantly reduces the activation barrier for proton transport. In isolated systems, (H2O)H+⋯H2O and (Im)H+⋯Im, the preferred orientation angle between the neighbouring molecules was 90°. From density functional molecular dynamics simulations of the bulk system, the proton diffusion coefficient was found to increase under the perturbation by the applied electric fields in range of 1.29 × 107 to 3.86 × 107 V cm−1 (0.0025–0.0075 a.u.) for both water and imidazole. To trace the efficient proton transfer, the proton movement trajectory was explicitly analysed in detail. Interestingly, a tilted proton hopping direction was found for imidazole crystal.
Ab initio calculation based on density functional theory was performed for studying high-pressure... more Ab initio calculation based on density functional theory was performed for studying high-pressure effects on the electronic properties and photoabsorption of Ga(1-x)Mn(x)As. Mn atom was substituted into the varied GaAs supercells, which observed the Mn concentrations at 3.70%, 8.33% and 12.50%. In zinc blende phase of Ga(1-x)Mn(x)As, we found that the effects of Mn on GaAs in the pressure range 0–10 GPa are the reducing of bandgap, generating of impurity peak and increasing of photoabsorption coefficient. The impurity peaks in Ga(1-x)Mn(x)As decrease under pressure increasing because the carriers were excited to conduction band by the effect of bond lengths reducing. The tendency of absorption coefficient of Ga(1-x)Mn(x)As in range of light-wavelength depends on size of impurity peak.
Imagery of ecological systems can be used to observe organisms, to observe rare events and to doc... more Imagery of ecological systems can be used to observe organisms, to observe rare events and to document long-term changes in ecological systems. Here we describe a system used for archiving and sharing imagery with ecological researchers Thailand, and present some examples of their use. The Coral Virtual System monitors a coral ecosystem at the Racha Island, Phuket, Thailand. The Coral
Ab initio calculations were performed for investigating the high pressure phases of GaAs upto 200... more Ab initio calculations were performed for investigating the high pressure phases of GaAs upto 200GPa. By comparing the minimum free energies of structures, we found the thermodynamically stable phases of GaAs under pressure beyond GaAs-III (Imm2) with space groups Pmma and P4/nmm at the pressure range of 88–146 GPa and 146-200GPa, respectively. For discussing the difference results of GaAs IV and V in previous studies, we found that Pmma and P4/nmm are the lower symmetric phases of P6/mmm and CsCl-like, respectively. For analyzing the Pmma-P4/nmm phase transition, we observed the approximated path and found that the barrier of transformation from Pmma to P4/nmm in direction [110] is 0.035 eV. The graph of density of states shows no energy gap in stable phases at 130 and 160 GPa, indicating that Pmma and P4/nmm are the metallic phases. The contour plots of the electron density difference show some valence electron sharing in Pmma which is higher than in P4/nmm. Moreover, the results of elastic parameters and modulus ratio suggested that the Pmma phase is a ductile material, while the P4/nmm phase is a brittle due to the increasing of shear modulus.
ABSTRACT Heath information across geographically distributed healthcare centers has been recogniz... more ABSTRACT Heath information across geographically distributed healthcare centers has been recognized as an essential resource that drives an efficient national health-care plan. There is thus a need for the National Health Information System (NHIS) that provides the transparent and secure access to health information from different healthcare centers both on demand and in a time efficient manner. As healthiness is the ultimate goal of people and nation, we believe that the NHIS should be sustainable by taking the healthcare center and information consumer perspectives into account. Several issues in particular must be resolved altogether: (i) the diversity of health information structures among healthcare centers; (ii) the availability of health information sharing from healthcare centers; (iii) the efficient information access to various healthcare centers; and (iv) the privacy and privilege of heath information. To achieve the sustainable NHIS, this paper details our work which is divided into 3 main phases. Essentially, the first phase focuses on the application of metadata standard to enable the interoperability and usability of health information across healthcare centers. The second phase moves forward to make information sharing possible and to provide an efficient information access to a large number of healthcare centers. Finally, in the third phase, the privacy and privilege of health information is promoted with respect to access rights of information consumers.
ABSTRACT This paper presents eInformatorium -- a one-stop and multi-faceted observation data serv... more ABSTRACT This paper presents eInformatorium -- a one-stop and multi-faceted observation data service. In particular, eInformatorium enables users to simply (i) acquire any observation data of interest across geographically distributed repositories via a single point access, and (ii) visualize any observation data of choice in a desirable graphical presentation on demand and in a user-oriented manner. The applicability of eInformatorium is currently evaluated by a few users. The result has shown that eInformatorium enables users to simply acquire the preferable visualized observation data in a time and budget efficient manner. It also leads them to further conduct detailed studies and decisions. Last but not least, beside users, eInformatorium encourages repository owners to register and share their belonging observation data.
The ground state and the lowest singlet excited-state geometries of poly-(9,9-dialkylfluorene-2,7... more The ground state and the lowest singlet excited-state geometries of poly-(9,9-dialkylfluorene-2,7-vinylene) copolymer or PFV and its derivatives (NH2–FV)n, (CN–FV)n, (OMe–FV)n and (OH–FV)n (n=2–5) were investigated based on density functional theory (DFT) and time-dependent DFT using B3LYP functional. The ground state and the lowest singlet excited-state geometries of the oligomers were optimized at the B3LYP/6-31G∗ and TD-B3LYP/SVP levels, respectively. The calculated
We used an ab initio method to calculate the high pressure phases of CuInSe2. By using the experi... more We used an ab initio method to calculate the high pressure phases of CuInSe2. By using the experimentally suggested phases, the enthalpy difference showed that the I-42d structure transforms into Fm-3m at 12 GPa and then into Cmcm at 42 GPa. The volume reductions at each phase transition are 13.9% and 1.9% respectively, compared with 11% and 1% from experiments. By using the sX-LDA functional, we found that the bandgap in the I-42d structure increases at the rate of 39.6 meV/GPa, in fair agreement with photoabsorption experiments. The band gap is closed in the Fm-3m and Cmcm structures. The bond lengths between Cu-Se and In–Se were investigated. We found that the bond lengths can be related to the behavior of the energy gap under high pressure. The path of transformation from Fm-3m to Cmcm was proposed. The energy barrier between the two phases was estimated. The upper bound of the energy barrier is 17 meV which is equivalent to 198 K. This finding can explain the existence of two phases at room temperature reported by experimental study.
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