This document discusses multiscale modeling of grain boundary segregation and embrittlement in tungsten alloys. A team led by Jian Luo at Clemson University and UC San Diego is developing multiscale modeling strategies to link grain boundary segregation to embrittlement. The team is using tungsten binary and ternary alloys as model systems. As part of the project, the team has computed ternary grain boundary lambda diagrams for W-Ni-X (X=Zr, Co, Cr, Fe, Nb, Ti) alloys to predict the tendency for grain boundary disordering. Experimental validation of the modeling shows the co-doping effect on promoting grain boundary disordering follows
Nucleation III: Phase-field crystal modeling of nucleation processDaniel Wheeler
This document summarizes research on modeling nucleation processes using phase-field crystal modeling. It begins with an introduction to complex polycrystalline structures that form through nucleation and growth processes. It then provides an overview of the phase-field crystal approach and how it can be used to model nucleation and growth dynamics. Specific applications discussed include modeling homogeneous and heterogeneous nucleation barriers using the Euler-Lagrange method and simulating non-equilibrium nucleation processes using the diffusive phase-field crystal model. The document highlights how phase-field crystal modeling can provide insights into precursor structures, growth morphologies, and freezing mechanisms observed in experiments.
Nucleation III: Phase-field crystal modeling of nucleation processPFHub PFHub
The document summarizes research on modeling nucleation processes using phase-field crystal modeling. It discusses how phase-field crystal models can capture nucleation and growth phenomena observed in experiments and atomistic simulations. Specifically, it describes how different phase-field crystal models are able to simulate:
1) Homogeneous and heterogeneous nucleation processes in 2D and 3D, including the effects of lattice mismatch and particle-induced nucleation.
2) Continuous cooling simulations that show amorphous phase formation prior to crystallization, similar to experimental observations in colloids.
3) Instantaneous quenching simulations that produce amorphous clusters and domains that facilitate heterogeneous nucleation of body-centered cubic crystals.
4
Theoretical and Applied Phase-Field: Glimpses of the activities in IndiaDaniel Wheeler
1. The document summarizes recent work on phase-field modeling from several research groups in India.
2. It describes applications of phase-field modeling to spinodal decomposition, grain growth, precipitate evolution, and multi-phase solidification.
3. It highlights a recent study by the author using phase-field modeling to predict the equilibrium shapes of coherent precipitates under the influence of elastic stresses. The model accounts for elastic anisotropy and different eigenstrain configurations.
Phase-field modeling of crystal nucleation: Comparison with simulations and e...PFHub PFHub
The document summarizes a talk on phase-field modeling of crystal nucleation. It compares simulations using single-field phase-field models to molecular dynamics simulations and experiments for various materials. For nickel, water, and a Lennard-Jones system, the "standard" phase-field model agrees well with the simulations and experiments. However, for a hard-sphere system, a different phase-field model based on Ginzburg-Landau theory is needed. Further theoretical work is required to develop phase-field models that can accurately describe crystal nucleation across different materials.
Phase-field modeling of crystal nucleation I: Fundamentals and methodsDaniel Wheeler
This document summarizes phase-field modeling of homogeneous crystal nucleation using two main methods. The first method adds fluctuations (noise) to the phase-field equations of motion to mimic natural nucleation. The noise amplitude is determined by the fluctuation-dissipation theorem. This models nucleation without assuming a sharp interface or bulk properties. The second method places supercritical crystal seeds randomly in space and time to model nucleation. Quantitative results from both methods are difficult to obtain due to limitations of classical nucleation theory. The document outlines the phase-field model and equations used to simulate homogeneous nucleation and crystal growth in 2D with and without noise to demonstrate convergence with spatial and temporal discretization.
The document discusses climate modeling and simulations performed at the German Climate Computing Center (DKRZ). It provides an overview of DKRZ's high performance computing capabilities and describes the components and coupling of Earth system models. It also summarizes simulations contributed to the CMIP5/IPCC AR5 project, including temperature and sea ice projections under different scenarios. Visualization of simulation output is discussed along with the Avizo Green software developed in collaboration with DKRZ.
Quantitative lithology an application for open and cased hamrhaggag
1) The document presents a new quantitative lithology interpretation method based on elemental concentrations from gamma ray spectroscopy logs.
2) It finds strong linear relationships between total clay concentration and the elemental concentrations of aluminum, silicon, calcium, and iron in core samples.
3) The method uses concentrations of silicon, calcium and iron to estimate clay content as accurately as using aluminum concentration, which is difficult to measure via logging. Example clay estimates are provided and show good agreement with core data.
Multi-phase-field simulations with OpenPhaseDaniel Wheeler
The document describes OpenPhase, an open-source phase field modeling toolbox for simulating microstructure evolution. OpenPhase uses a multi-phase field approach and includes modules for simulating processes like coarsening, diffusion, deformation, plasticity, damage, and fluid flow. It has been under development for over 10 years. The document provides an overview of OpenPhase capabilities and includes an example of using it to simulate Mg-Al alloy solidification, comparing experimental and simulated microstructures. It also gives details about setting up and running a simulation using the OpenPhase modules in C++.
Nucleation III: Phase-field crystal modeling of nucleation processDaniel Wheeler
This document summarizes research on modeling nucleation processes using phase-field crystal modeling. It begins with an introduction to complex polycrystalline structures that form through nucleation and growth processes. It then provides an overview of the phase-field crystal approach and how it can be used to model nucleation and growth dynamics. Specific applications discussed include modeling homogeneous and heterogeneous nucleation barriers using the Euler-Lagrange method and simulating non-equilibrium nucleation processes using the diffusive phase-field crystal model. The document highlights how phase-field crystal modeling can provide insights into precursor structures, growth morphologies, and freezing mechanisms observed in experiments.
Nucleation III: Phase-field crystal modeling of nucleation processPFHub PFHub
The document summarizes research on modeling nucleation processes using phase-field crystal modeling. It discusses how phase-field crystal models can capture nucleation and growth phenomena observed in experiments and atomistic simulations. Specifically, it describes how different phase-field crystal models are able to simulate:
1) Homogeneous and heterogeneous nucleation processes in 2D and 3D, including the effects of lattice mismatch and particle-induced nucleation.
2) Continuous cooling simulations that show amorphous phase formation prior to crystallization, similar to experimental observations in colloids.
3) Instantaneous quenching simulations that produce amorphous clusters and domains that facilitate heterogeneous nucleation of body-centered cubic crystals.
4
Theoretical and Applied Phase-Field: Glimpses of the activities in IndiaDaniel Wheeler
1. The document summarizes recent work on phase-field modeling from several research groups in India.
2. It describes applications of phase-field modeling to spinodal decomposition, grain growth, precipitate evolution, and multi-phase solidification.
3. It highlights a recent study by the author using phase-field modeling to predict the equilibrium shapes of coherent precipitates under the influence of elastic stresses. The model accounts for elastic anisotropy and different eigenstrain configurations.
Phase-field modeling of crystal nucleation: Comparison with simulations and e...PFHub PFHub
The document summarizes a talk on phase-field modeling of crystal nucleation. It compares simulations using single-field phase-field models to molecular dynamics simulations and experiments for various materials. For nickel, water, and a Lennard-Jones system, the "standard" phase-field model agrees well with the simulations and experiments. However, for a hard-sphere system, a different phase-field model based on Ginzburg-Landau theory is needed. Further theoretical work is required to develop phase-field models that can accurately describe crystal nucleation across different materials.
Phase-field modeling of crystal nucleation I: Fundamentals and methodsDaniel Wheeler
This document summarizes phase-field modeling of homogeneous crystal nucleation using two main methods. The first method adds fluctuations (noise) to the phase-field equations of motion to mimic natural nucleation. The noise amplitude is determined by the fluctuation-dissipation theorem. This models nucleation without assuming a sharp interface or bulk properties. The second method places supercritical crystal seeds randomly in space and time to model nucleation. Quantitative results from both methods are difficult to obtain due to limitations of classical nucleation theory. The document outlines the phase-field model and equations used to simulate homogeneous nucleation and crystal growth in 2D with and without noise to demonstrate convergence with spatial and temporal discretization.
The document discusses climate modeling and simulations performed at the German Climate Computing Center (DKRZ). It provides an overview of DKRZ's high performance computing capabilities and describes the components and coupling of Earth system models. It also summarizes simulations contributed to the CMIP5/IPCC AR5 project, including temperature and sea ice projections under different scenarios. Visualization of simulation output is discussed along with the Avizo Green software developed in collaboration with DKRZ.
Quantitative lithology an application for open and cased hamrhaggag
1) The document presents a new quantitative lithology interpretation method based on elemental concentrations from gamma ray spectroscopy logs.
2) It finds strong linear relationships between total clay concentration and the elemental concentrations of aluminum, silicon, calcium, and iron in core samples.
3) The method uses concentrations of silicon, calcium and iron to estimate clay content as accurately as using aluminum concentration, which is difficult to measure via logging. Example clay estimates are provided and show good agreement with core data.
Multi-phase-field simulations with OpenPhaseDaniel Wheeler
The document describes OpenPhase, an open-source phase field modeling toolbox for simulating microstructure evolution. OpenPhase uses a multi-phase field approach and includes modules for simulating processes like coarsening, diffusion, deformation, plasticity, damage, and fluid flow. It has been under development for over 10 years. The document provides an overview of OpenPhase capabilities and includes an example of using it to simulate Mg-Al alloy solidification, comparing experimental and simulated microstructures. It also gives details about setting up and running a simulation using the OpenPhase modules in C++.
This document summarizes evidence for the past and present distribution of water on Mars in its three phases - solid, liquid, and vapor. It discusses the theoretical and observational evidence for each phase, including calculations of the depth of the Martian cryosphere based on thermal modeling, constitutive relations for ice deformation, comparisons of Martian and terrestrial rock glaciers, and analysis of slope asymmetry in polar layered deposits indicating differential sublimation erosion of ice-rich material. Spatial and temporal variations in atmospheric water vapor from early telescopic observations through recent TES data are also summarized.
This document provides an update on Benchmark 6, which models the flow of a charged concentration field using a coupled Cahn-Hilliard-Poisson formulation. The previous formulation was unsatisfactory, so changes were made to make the model more physical and different from a block co-polymer problem. The new formulation includes a concentration-dependent mobility, neutralizing background charge, applied external field, and zero particle and charge flow boundary conditions. Some tests were run in MOOSE to check that the solution behaves reasonably by tuning parameters like the dielectric constant and mobility.
Palestra plenária do XI Encontro da SBPMat (Florianópolis, setembro de 2012). Palestrante: Mrityunjay Singh - Instituto Aeroespacial de Ohio, ligado ao Centro de Pesquisa Glenn da NASA (EUA).
Optical Control of Selectivity of High Rate CO2 Photoreduction Via Interband-...Pawan Kumar
Photonic crystals consisting of TiO2 nanotube arrays (PMTiNTs) with periodically modulated diameters were fabricated using a precise charge-controlled pulsed anodization technique. The PMTiNTs were decorated with gold nanoparticles (Au NPs) to form plasmonic photonic crystal photocatalysts (Au-PMTiNTs). A systematic study of CO2 photoreduction performance on as-prepared samples was conducted using different wavelengths and illumination sequences. A remarkable selectivity of the mechanism of CO2 photoreduction could be engineered by merely varying the spectral composition of the illumination sequence. Under AM1.5 G simulated sunlight (pathway#1), the Au-PMTiNTs produced methane (302 µmol h-1) from CO2 with high selectivity (89.3%). When also illuminated by a UV-poor white lamp (pathway#2), the Au-PMTiNTs produced formaldehyde (420 µmol h-1) and carbon monoxide (323 µmol h-1) with almost no methane evolved. We confirmed the photoreduction results by 13C isotope labeling experiments using GC-MS. These results point to optical control of the selectivity of high-rate CO2 photoreduction through selection of one of two different mechanistic pathways. Pathway#1 implicates electron-hole pairs generated through interband transitions in TiO2 and Au as the primary active species responsible for reducing CO2 to methane. Pathway#2 involves excitation of both TiO2 and surface plasmons in Au. Hot electrons produced by plasmon damping and photogenerated holes in TiO2 proceed to reduce CO2 to HCHO and CO through a plasmonic Z-scheme.
International Journal of Engineering Research and Applications (IJERA) aims to cover the latest outstanding developments in the field of all Engineering Technologies & science.
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
1) The document discusses using the effective one body (EOB) formalism to model gravitational wave templates for LIGO and LISA. It summarizes the number and type of templates used in LIGO's first two observing runs.
2) It also discusses using EOB, post-Newtonian theory, numerical relativity simulations, and quantum field theory to model gravitational wave emission from binary black hole and binary neutron star mergers across different mass ratio and velocity regimes.
3) The document focuses on recent work extending EOB models to higher post-Minkowskian orders and including the effects of spin and tidal interactions, with the goal of more accurate gravitational wave template modeling.
Structural aspect on carbon dioxide capture in nanotubesIJRES Journal
In this work we reported the carbon dioxide adsorption (CO2) in six different nanostructures in order
to investigate the capturing capacity of the materials at nanoscale. Here we have considered the three different
nanotubes including zinc oxide nanotube (ZnONT), silicon carbide nanotube (SiCNT) and single walled carbon
nanotube (SWCNT). Three different chiralities such as zigzag (9,0), armchair (5,5) and chiral (6,4) having
approximately same diameter are analyzed. The adsorption binding energy values under various cases are
estimated with density functional theory (DFT). We observed CO2 molecule chemisorbed on ZnONT and
SiCNT’s whereas the physisorption is predominant in CNT. To investigate the structural aspect, the tubes with
defects are studied and compared with defect free tubes. We have also analyzed the electrical properties of tubes
from HOMO, LUMO energies. Our results reveal the defected structure enhance the CO2 capture and is
predicted to be a potential candidate for environmental applications.
Localized Electrons with Wien2k
LDA+U, EECE, MLWF, DMFT
Elias Assmann
Vienna University of Technology, Institute for Solid State Physics
WIEN2013@PSU, Aug 14
Grb 130606a as_a_probe_of_the_intergalactic_medium_and_the_interstelar_medium...Sérgio Sacani
This document summarizes observations of the gamma-ray burst GRB 130606A at a redshift of z=5.913 using spectroscopy from the MMT and Gemini telescopes. The high quality spectra exhibit a smooth near-infrared continuum that is sharply cut off by Lyman-alpha absorption at z=5.91, with some flux transmitted through the Lyman-alpha forest at lower redshifts. Metal absorption lines in the host galaxy are used to constrain its metallicity between -1.7 and -0.5 solar. Transmission in the Lyman-alpha forest is found to evolve consistently with previous quasar observations. An extended region at z=5.77 shows no Lyman-alpha transmission,
The document summarizes research on simulating the surface tension of liquid nickel through molecular dynamics and density functional theory calculations. It describes using embedded atom method interatomic potentials to model nickel, compares calculated density-temperature data to experimental values, and presents a molecular dynamics simulation of a molten nickel nanoparticle in good agreement with experiment. Future work is outlined on modeling nickel-aluminum alloys, oxidation effects, and temperature-dependent interdiffusion at metal-metal interfaces.
Phase-field modeling of crystal nucleation II: Comparison with simulations an...PFHub PFHub
This document summarizes phase-field modeling of crystal nucleation. It discusses:
1) Homogeneous nucleation models using the phase-field method and their comparison to molecular dynamics simulations and experiments for systems like nickel and Lennard-Jones argon.
2) Applications of the phase-field model to heterogeneous systems like ice-water nucleation.
3) The effects of different double-well and interpolation functions on nucleation behavior in phase-field models.
The document analyzes seasonal signals in GPS time series data. It categorizes signals into gravitational, thermal, and error sources. It finds that pole tide explains most of the observed annual vertical variation in site positions. Additional modeled contributions from atmospheric mass, non-tidal ocean mass, snow mass, and soil moisture explain 66% of observed power. Remaining signals may be due to errors in models or processing, or unmodeled geophysical effects like bedrock expansion.
El documento busca contratar a un ingeniero junior en informática o telecomunicaciones para trabajar en el desarrollo de herramientas TIC relacionadas con la salud y la asistencia social. El puesto implica aprender sobre procesado de señales biomédicas, análisis de datos e inteligencia artificial para mejorar la atención sanitaria de forma eficiente. Se busca a alguien recién titulado con conocimientos en programación, procesado digital de señales y nivel B2 de inglés.
This document provides information about Python version 2.6.5, including copyright details, license information, what's new in the release, how to learn and use Python, documentation, websites, mailing lists, bug reporting, contributions, questions, and build instructions for various platforms. It summarizes the key points about Python, how to get started, where to find help and documentation, and how to build and install Python on different systems.
El documento presenta varios juegos de lógica y problemas de razonamiento que involucran mover objetos o personas de un lado a otro bajo ciertas restricciones, como intercambiar ranas de colores, ayudar a cruzar animales de un granjero respetando su dieta, ayudar a misioneros y caníbales a cruzar un lago sin que se coman entre sí, y ayudar a una familia a cruzar un puente con una linterna bajo restricciones de velocidad y capacidad del puente.
This is an updated version of my Mobile Tsunami presentation. The presentation includes a detailed analysis pf the main trends in the mobile market, mobile usage habits, app usage habits etc. All the numbers have been updated to May 2011
O documento fornece informações sobre moradia para imigrantes brasileiros em Vancouver, Canadá. Explica que os aluguéis variam de $700 a $2200 dependendo do tamanho e localização do imóvel. Detalha os tipos comuns de moradias como apartamentos, duplex e quartos para alugar. Discutem contratos de locação e depósitos de segurança.
The document discusses testing the weak form efficient market hypothesis for four stock market indexes: DFM, MSM 30, S&P/ASX 200, and Euro Stoxx 50. Statistical tests including descriptive statistics, run tests of randomness, and least squares regression were used.
The results showed that DFM and MSM 30 indexes failed the run test, indicating they do not follow random walks and are not weak form efficient. Meanwhile, the S&P/ASX 200 and Euro Stoxx 50 indexes passed the run test, showing they are weak form efficient. Additional least squares regression was used to confirm the run test results.
Mayor's Economic Development Commission presentationMatthew Crane
The mayor of Jasper presented on current and potential economic development projects and initiatives in the city. There are many ongoing and planned projects focused on improving infrastructure, developing a sense of place, and promoting the city. Projects include developing the downtown and riverfront areas, renovating old buildings, expanding trails and parks, conducting transportation and utility studies, and strengthening partnerships. The goal is to connect all projects and growth, avoid isolated initiatives, and continue building momentum to attract new residents and businesses to Jasper.
This document summarizes evidence for the past and present distribution of water on Mars in its three phases - solid, liquid, and vapor. It discusses the theoretical and observational evidence for each phase, including calculations of the depth of the Martian cryosphere based on thermal modeling, constitutive relations for ice deformation, comparisons of Martian and terrestrial rock glaciers, and analysis of slope asymmetry in polar layered deposits indicating differential sublimation erosion of ice-rich material. Spatial and temporal variations in atmospheric water vapor from early telescopic observations through recent TES data are also summarized.
This document provides an update on Benchmark 6, which models the flow of a charged concentration field using a coupled Cahn-Hilliard-Poisson formulation. The previous formulation was unsatisfactory, so changes were made to make the model more physical and different from a block co-polymer problem. The new formulation includes a concentration-dependent mobility, neutralizing background charge, applied external field, and zero particle and charge flow boundary conditions. Some tests were run in MOOSE to check that the solution behaves reasonably by tuning parameters like the dielectric constant and mobility.
Palestra plenária do XI Encontro da SBPMat (Florianópolis, setembro de 2012). Palestrante: Mrityunjay Singh - Instituto Aeroespacial de Ohio, ligado ao Centro de Pesquisa Glenn da NASA (EUA).
Optical Control of Selectivity of High Rate CO2 Photoreduction Via Interband-...Pawan Kumar
Photonic crystals consisting of TiO2 nanotube arrays (PMTiNTs) with periodically modulated diameters were fabricated using a precise charge-controlled pulsed anodization technique. The PMTiNTs were decorated with gold nanoparticles (Au NPs) to form plasmonic photonic crystal photocatalysts (Au-PMTiNTs). A systematic study of CO2 photoreduction performance on as-prepared samples was conducted using different wavelengths and illumination sequences. A remarkable selectivity of the mechanism of CO2 photoreduction could be engineered by merely varying the spectral composition of the illumination sequence. Under AM1.5 G simulated sunlight (pathway#1), the Au-PMTiNTs produced methane (302 µmol h-1) from CO2 with high selectivity (89.3%). When also illuminated by a UV-poor white lamp (pathway#2), the Au-PMTiNTs produced formaldehyde (420 µmol h-1) and carbon monoxide (323 µmol h-1) with almost no methane evolved. We confirmed the photoreduction results by 13C isotope labeling experiments using GC-MS. These results point to optical control of the selectivity of high-rate CO2 photoreduction through selection of one of two different mechanistic pathways. Pathway#1 implicates electron-hole pairs generated through interband transitions in TiO2 and Au as the primary active species responsible for reducing CO2 to methane. Pathway#2 involves excitation of both TiO2 and surface plasmons in Au. Hot electrons produced by plasmon damping and photogenerated holes in TiO2 proceed to reduce CO2 to HCHO and CO through a plasmonic Z-scheme.
International Journal of Engineering Research and Applications (IJERA) aims to cover the latest outstanding developments in the field of all Engineering Technologies & science.
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
1) The document discusses using the effective one body (EOB) formalism to model gravitational wave templates for LIGO and LISA. It summarizes the number and type of templates used in LIGO's first two observing runs.
2) It also discusses using EOB, post-Newtonian theory, numerical relativity simulations, and quantum field theory to model gravitational wave emission from binary black hole and binary neutron star mergers across different mass ratio and velocity regimes.
3) The document focuses on recent work extending EOB models to higher post-Minkowskian orders and including the effects of spin and tidal interactions, with the goal of more accurate gravitational wave template modeling.
Structural aspect on carbon dioxide capture in nanotubesIJRES Journal
In this work we reported the carbon dioxide adsorption (CO2) in six different nanostructures in order
to investigate the capturing capacity of the materials at nanoscale. Here we have considered the three different
nanotubes including zinc oxide nanotube (ZnONT), silicon carbide nanotube (SiCNT) and single walled carbon
nanotube (SWCNT). Three different chiralities such as zigzag (9,0), armchair (5,5) and chiral (6,4) having
approximately same diameter are analyzed. The adsorption binding energy values under various cases are
estimated with density functional theory (DFT). We observed CO2 molecule chemisorbed on ZnONT and
SiCNT’s whereas the physisorption is predominant in CNT. To investigate the structural aspect, the tubes with
defects are studied and compared with defect free tubes. We have also analyzed the electrical properties of tubes
from HOMO, LUMO energies. Our results reveal the defected structure enhance the CO2 capture and is
predicted to be a potential candidate for environmental applications.
Localized Electrons with Wien2k
LDA+U, EECE, MLWF, DMFT
Elias Assmann
Vienna University of Technology, Institute for Solid State Physics
WIEN2013@PSU, Aug 14
Grb 130606a as_a_probe_of_the_intergalactic_medium_and_the_interstelar_medium...Sérgio Sacani
This document summarizes observations of the gamma-ray burst GRB 130606A at a redshift of z=5.913 using spectroscopy from the MMT and Gemini telescopes. The high quality spectra exhibit a smooth near-infrared continuum that is sharply cut off by Lyman-alpha absorption at z=5.91, with some flux transmitted through the Lyman-alpha forest at lower redshifts. Metal absorption lines in the host galaxy are used to constrain its metallicity between -1.7 and -0.5 solar. Transmission in the Lyman-alpha forest is found to evolve consistently with previous quasar observations. An extended region at z=5.77 shows no Lyman-alpha transmission,
The document summarizes research on simulating the surface tension of liquid nickel through molecular dynamics and density functional theory calculations. It describes using embedded atom method interatomic potentials to model nickel, compares calculated density-temperature data to experimental values, and presents a molecular dynamics simulation of a molten nickel nanoparticle in good agreement with experiment. Future work is outlined on modeling nickel-aluminum alloys, oxidation effects, and temperature-dependent interdiffusion at metal-metal interfaces.
Phase-field modeling of crystal nucleation II: Comparison with simulations an...PFHub PFHub
This document summarizes phase-field modeling of crystal nucleation. It discusses:
1) Homogeneous nucleation models using the phase-field method and their comparison to molecular dynamics simulations and experiments for systems like nickel and Lennard-Jones argon.
2) Applications of the phase-field model to heterogeneous systems like ice-water nucleation.
3) The effects of different double-well and interpolation functions on nucleation behavior in phase-field models.
The document analyzes seasonal signals in GPS time series data. It categorizes signals into gravitational, thermal, and error sources. It finds that pole tide explains most of the observed annual vertical variation in site positions. Additional modeled contributions from atmospheric mass, non-tidal ocean mass, snow mass, and soil moisture explain 66% of observed power. Remaining signals may be due to errors in models or processing, or unmodeled geophysical effects like bedrock expansion.
El documento busca contratar a un ingeniero junior en informática o telecomunicaciones para trabajar en el desarrollo de herramientas TIC relacionadas con la salud y la asistencia social. El puesto implica aprender sobre procesado de señales biomédicas, análisis de datos e inteligencia artificial para mejorar la atención sanitaria de forma eficiente. Se busca a alguien recién titulado con conocimientos en programación, procesado digital de señales y nivel B2 de inglés.
This document provides information about Python version 2.6.5, including copyright details, license information, what's new in the release, how to learn and use Python, documentation, websites, mailing lists, bug reporting, contributions, questions, and build instructions for various platforms. It summarizes the key points about Python, how to get started, where to find help and documentation, and how to build and install Python on different systems.
El documento presenta varios juegos de lógica y problemas de razonamiento que involucran mover objetos o personas de un lado a otro bajo ciertas restricciones, como intercambiar ranas de colores, ayudar a cruzar animales de un granjero respetando su dieta, ayudar a misioneros y caníbales a cruzar un lago sin que se coman entre sí, y ayudar a una familia a cruzar un puente con una linterna bajo restricciones de velocidad y capacidad del puente.
This is an updated version of my Mobile Tsunami presentation. The presentation includes a detailed analysis pf the main trends in the mobile market, mobile usage habits, app usage habits etc. All the numbers have been updated to May 2011
O documento fornece informações sobre moradia para imigrantes brasileiros em Vancouver, Canadá. Explica que os aluguéis variam de $700 a $2200 dependendo do tamanho e localização do imóvel. Detalha os tipos comuns de moradias como apartamentos, duplex e quartos para alugar. Discutem contratos de locação e depósitos de segurança.
The document discusses testing the weak form efficient market hypothesis for four stock market indexes: DFM, MSM 30, S&P/ASX 200, and Euro Stoxx 50. Statistical tests including descriptive statistics, run tests of randomness, and least squares regression were used.
The results showed that DFM and MSM 30 indexes failed the run test, indicating they do not follow random walks and are not weak form efficient. Meanwhile, the S&P/ASX 200 and Euro Stoxx 50 indexes passed the run test, showing they are weak form efficient. Additional least squares regression was used to confirm the run test results.
Mayor's Economic Development Commission presentationMatthew Crane
The mayor of Jasper presented on current and potential economic development projects and initiatives in the city. There are many ongoing and planned projects focused on improving infrastructure, developing a sense of place, and promoting the city. Projects include developing the downtown and riverfront areas, renovating old buildings, expanding trails and parks, conducting transportation and utility studies, and strengthening partnerships. The goal is to connect all projects and growth, avoid isolated initiatives, and continue building momentum to attract new residents and businesses to Jasper.
The document appears to be a quiz containing multiple choice and fill-in-the-blank questions related to current events, business, and popular culture. It includes questions about a popular item in India, a failed Bitcoin exchange, an app that was hacked, an Indian film, companies and brands. The questions cover topics in technology, entertainment, sports, and world news from 2013-2014.
Este documento é uma edição da Revista da Propriedade Industrial publicada pelo Instituto Nacional da Propriedade Industrial do Brasil. A revista contém informações sobre patentes, desenhos industriais, contratos de tecnologia, indicações geográficas e registros correlatos.
O documento resume as principais funções e ações da Controladoria-Geral da União (CGU), órgão responsável pelo controle interno do governo federal brasileiro. A CGU atua na prevenção e combate à corrupção, no fortalecimento da gestão pública e na promoção da transparência e do controle social.
O documento descreve as competências e formas de atuação da Controladoria-Geral da União (CGU). A CGU é responsável por atividades de controle interno, auditoria pública, correição e combate à corrupção no Poder Executivo Federal. Sua atuação inclui monitoramento da Lei de Acesso à Informação, fiscalização contábil e financeira, e apoio ao controle externo exercido pelo Congresso Nacional.
O documento descreve a 1a Conferência Nacional sobre Transparência e Controle Social (Consocial) organizada pela Controladoria-Geral da União (CGU). A Consocial tem como objetivo promover o debate sobre transparência pública, controle social e prevenção à corrupção entre o governo, sociedade civil e demais atores. O documento apresenta a comissão organizadora, os eixos temáticos, as etapas do evento e convida à participação na conferência.
This document describes a company called ECOnomic Housing that provides economic and ecologic housing solutions for Angola. It discusses their services including procurement, engineering, construction management. It then outlines their smart building concept using a modular steel frame that requires no cement or welding. Several designs for houses in Angola are presented, including a 110m2 two-story design and designs for navy housing that are adaptable and relocatable. Their services for housing projects and expertise in area development such as urban planning, energy, and infrastructure are also summarized.
USTDA aims to advance economic development and US commercial interests in developing countries. It has a dual mission as a foreign assistance agency and trade promotion agency. It provides funding for investment analysis, feasibility studies, technical assistance, and reverse trade missions to enable investments in infrastructure and support a fair trading environment. USTDA evaluates projects based on their developmental priority, likelihood of implementation funding, and potential for US exports. It has numerous success stories funding projects in Sub-Saharan Africa focused on energy, transportation, and other infrastructure sectors.
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2. Jian Luo
This UCR Project
Develop multiscale modeling
strategies to link GB segregation with
GB embrittlement
Tomar et al. at Purdue
Develop thermodynamic theories
and models to predict
a “new” type of high‐T
(premelting‐like)
GB segregation
Luo et al. at Clemson/UCSD
Ternary W‐Ni‐X
(X = Zr, Co, Cr, Fe, Nb, Ti)
GB ‐diagrams
Experimental
validation
Selected Results from Our Year‐3 Efforts
Using tungsten (W) based binary & ternary alloys as model systems…
Atomistic &
quantum
modeling of
stress‐strain
Continuum
facture modeling
Phonon Dispersion
GB = Grain Boundary
3. Jian Luo
Background: Grain Boundary (GB) Segregation
The Classical Models vs. New Perspectives
kT
g
C
C
ads
e
X
X
10
McLean-Langmuir: Fowler-Guggenheim:
0
Fowler1
)0(
zgg adsads
Reprint from Luo,
J. Am. Ceram. Soc. 95:2358 (2012)
4. Jian Luo
Classical GB Embrittlement Models – Built on Langmuir‐McLean Adsorption
Interfacial Disordering
(Liquid‐Like GB “Complexion”)
2 nm2 nm
Mo-Ni W-Ni
Acta Mater. 55, 3131 (2007)APL 94, 251908 (2009)
New Perspective:
Segregation GB Transition Drastic Change in Properties
S segregation GB “melting” if CS
GB > 15%
GB Embrittlement
Atomistic Simulation: Chen et al., PRL 2010
Auger: Heuer et al., J. Nuclear Mater. 2002
S induced
GB “melting”
Reduction of cohesion due to:
• Electronic effect (weakening the bonds);
• Atomic size (strain) effect; or
• Changing relative ’s (the Rice-Wang Model)
Background: Grain Boundary (GB) Embrittlement
The Classical Models vs. New Perspectives
“Complexion” Transition
(Bilayer)
Luo, Cheng, Asl, Kiely & Harmer
Science 333:1730 (2011)
At High Temperatures & Alloying/Impurity Levels…
Segregation GB “Melting” (Interfacial Disordering) Embrittlement
Cu-Bi
Duscher, Chisholm, Alber & Rühle
Nature Mater. 3, 621 (2004)
Beyond
“Monolayer”
?
Ni-S
5. Jian Luo
Thermodynamically stable at
T < Tmelting
Multicomponent?
• Enhanced by segregation
Sintering (Prior work)
Embrittlement (This study)
Coble creep? (Next UCR project)
The Phenomenon
Can be stabilized at
T < Tsolidus
Unary Systems:
• Surface Premelting
• GB Premelting ???
Late 1980’s: Balluffi’s group suggested no
GB premelting up to 0.999Tmelt in Al!
hGamorph.ZnO ZnO
ZnOVapor
W
W
Ni-enriched
film
T Teutectic – T = 140C T = 40C T = 95C
Ceramic Systems (Well Known) Ni-doped W
Bi2O3-enriched film
Luo et al, APL 2005Wang & Chiang, JAmCerS 1998Luo et al., Langmuir 2005
1 nm 1 nm 1 nm
Ice Surface (MD simultaion)
Dash et al, Rev. Modern Phys. 2006
GB premelting in a colloidal crystal
Alsayed et al, Science 2005
1400 C
6. Jian Luo
Thermodynamic Principle and Model
h (undercooled liquid)
A subsolidus quasi-liquid film is
thermodynamically stable if: clgbhG 2)0(
amorph
forming
undercooled liquid
solidus
interfacial ( )h
amorphG
Define & quantify:
Statistical
Thermodynamic Model
represents
the thermodynamic tendency to
stabilize a quasi‐liquid film
7. Jian Luo
Experimental
Validation:
• HRTEM
• Auger
• Onset Tsinter
for W-X
• DGB(T, X)
W‐Pd W‐Co W‐Fe
W‐Ni
A Prior Successful Example of Predictive Modeling: Extending Bulk CalPhaD Methods to GBs
Computed Lines of Constant : GB -Diagrams
Mo
+ 0.5 % Ni
8. Jian Luo
Practical Importance:
• Engineering alloys often have many components or impurities
• Co‐alloying to control GB behaviors?
Statistical Thermodynamic Model (using CalPhaD data)
Ternary
CalPhaD
ABC
CBA
n
j
j
AC
CA
jAC
n
j
j
CB
BC
jCB
n
j
j
BA
AB
jBACCBBAACCBBAABA
f
GXXXXXXXXXXX
XXXXXXXXXXRTGXGXGXXXTG
CABC
AB
00
0
000
)()(
)()lnlnln(),,(
Max
2
∆
∆
Redlich‐Kister
Expansion
1.9
2
/
3
/
One Major 3rd-Year Task of This UCR Project (as proposed)
Computing Ternary GB -Diagrams for W-Ni-X (X = Zr, Co, Cr, Fe, Nb, Ti)
9. Jian Luo
Construct A Ternary GB -Diagram
(An Example: W‐Ni‐Fe, 1300 C)
Considering ONLY the
W-based BCC phase
(& liquid phase)
Considering All Phases
@ Bulk Equilibria
0.1 0.2 0.3 0.4
0.5
1.0
1.5
2.0
2.5
W
Fe(%)
Ni (%)
BCC + FCC + ‐FeW
BCC +
BCC + FCC
BCC0.1 0.2 0.3 0.4
0.5
1.0
1.5
2.0
2.5
W
Fe(%)
Ni (%)
10. Jian Luo
Computed W-Ni-X (X = Cr, Zr, Co, Fe, Nb, Ti)
Ternary GB -Diagram
(Considering Only BCC and Liquid Phases)
T = 1300
0.1 0.2 0.3 0.4
0.5
1.0
1.5
2.0
2.5
Nb(%)
Ni (%)W
0.1 0.2 0.3 0.4
0.5
1.0
1.5
2.0
2.5
W
Zr(%)
Ni (%)
0.1 0.2 0.3 0.4
0.5
1.0
1.5
2.0
2.5
WTi(%) Ni (%)0.1 0.2 0.3 0.4
0.5
1.0
1.5
2.0
2.5
W
Fe(%)
Ni (%)
0.1 0.2 0.3 0.4
0.5
1.0
1.5
2.0
2.5
W
Cr(%)
Ni (%) 0.1 0.2 0.3 0.4
0.5
1.0
1.5
2.0
2.5
W
Co(%)
Ni (%)
BCC1 +BCC2
BCC BCC + Liquid
BCC + LiquidBCC + Liquid
BCC + LiquidBCC + LiquidBCC + Liquid
BCC1
+BCC2
BCC
BCC
BCC
BCC BCC
11. Jian Luo
Computed W-Ni-X (X = Cr, Zr, Co Fe, Nb, Ti)
Ternary GB -Diagram
(Considering All Stable Bulk Phases) T = 1300 C
0.1 0.2 0.3 0.4
0.5
1.0
1.5
2.0
2.5
W
Zr(%)
Ni (%)
BCC + ZrW2
BCC
+ FCC
BCC + FCC
+ ZrW2
BCC0.1 0.2 0.3 0.4
0.5
1.0
1.5
2.0
2.5
W
Cr(%)
Ni (%)
BCC
BCC + FCC
0.1 0.2 0.3 0.4
0.5
1.0
1.5
2.0
2.5
W
Co(%)
Ni (%)
BCC + FCC
+ Co7W6
BCC + FCC
BCC + Co7W6
0.1 0.2 0.3 0.4
0.5
1.0
1.5
2.0
2.5
W
Fe(%)
Ni (%)
BCC + FCC
+ ‐FeW
BCC +
BCC + FCC
0.1 0.2 0.3 0.4
0.5
1.0
1.5
2.0
2.5
W
Nb(%)
Ni (%)
BCC + Liquid
BCC + FCC
BCC + Ni3Nb
0.1 0.2 0.3 0.4
0.5
1.0
1.5
2.0
2.5
W
Ti(%)
Ni (%)
BCC + Liquid
BCC + Ni3Ti
BCC + FCC
BCC
BCC
BCC
One Prediction: The co‐alloying effect on promoting GB disordering of W‐Ni‐X
(represented by the increase in ) roughly follows the order: Cr < Zr < Co < Fe < Nb <Ti
12. Jian Luo
Experimental Model Validation: Co-doping Effects in Ternary Alloys
For W‐Ni‐X (X = Zr, Co, Cr, Fe, Nb, Ti)
0.5Ni 1Ni Cr Zr Co Fe Nb Ti
25
30
35
40
45
50
(nm)
densityincrease(%)
0
2
4
20
A custom‐made furnace
• To remove ramping effects
Increase in Relative Density (%)
X =
Ternary W‐0.5Ni‐0.5X (at. %)
Binary W‐Ni
Our Approach:
Density rate The effect of co‐alloying on promoting GB
disordering (represented by the increase in computed )
Limitation: Chemical effect on GB diffusion not represented
The only
exception in
rankings
13. Jian Luo
Estimate Interfacial Width (hEQ) from the Computed -Diagram?
W-Ni
1 nm
W-Ni
Estimating hEQ (& GB)
Ni‐Saturated W
(1400 C)
)()( amorphlinterfaciaamorph
)0(
hfhGhhGG gb
x
Interfacial
coefficient
1)(
0)0(
f
fThe Excess Free Energy: Interfacial (disjoining)
Potential
Continuum approx.
for metals:
)/ln( EQh
/
1)( h
ehf
Coherent length
GB -Diagram
14. Jian Luo
High-T (Liquid-Like) vs. Classic (Solid-Like) GB Segregation
(To Establish a Unified Thermodynamic Framework?)
W-Ni
1 nm
W-Ni
Premelting‐Like Segregation
Interfacial Disordering
Multilayer Segregation on the Lattice
Wynblatt‐Chatain [JMS 2005; 2006, MMA 2006]
Generally, more reduction
in the GB energies (GB’s)
for forming liquid‐like
complexions in W‐Ni and
most other W‐based alloys
(due to the high GB
0 of W)
15. Jian Luo
Useful Materials Science Tool for Designing:
• Fabrication protocols utilizing appropriate GB
structures to achieve optimal microstructures
• Co-doping strategies and/or heat treatment recipes
to tune the GB structures for desired performance
Applications: To predict useful trends in:
• GB embrittlement
• Sintering
• Grain growth & microstructural involution
• Coble creep
• GB controlled corrosion & oxidation
• …
A Useful Component for the “Materials Genome” Project?
Construct “Grain Boundary (GB) Diagrams”
More Rigorous GB
Complexion (“Phase”)
Diagrams ???
Prior work : Straumal et al., Interf. Sci. 2004; Tang et al., PRL 2006; Dillon et al. Acta Mater. 2007 & more
Following the late Dr. R. M. Cannon’s transformative concept
GB -Diagrams
(To Predict Useful Trends for GBs to Disorder)
A tentative GB
complexion
diagram for
adsorption
transitions
(calculated by
Wynblatt‐Chatain
Model; interfacial
disordering not
yet considered)
16. Jian Luo
Summary – Thermodynamics Thrust
We have …
• (Years 1 & 2) Derived the basic equations;
• (Years 1 & 2) Developed and tested the algorithms and MATLAB
codes;
• (Years 2) Completed numerical experiments;
• (Year 3) Computed “GB -diagrams” for W-Ni-X (X = Cr, Zr, Co, Fe,
Nb & Ti) systems;
• (Year 3) Conducted experimental validation for ternary W alloys;
• (Year 3) Compared with classical segregation model in an effort to
establish a unified framework; and
• Worked closely with the Purdue team to use our thermodynamic
models and experimental results to support their multiscale
modeling efforts to link GB segregation to mechanical properties.
17. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
The primary site of embrittlement of Nickel (Ni) – doped Tungsten (W) is
at the grain boundary (GB).
GB is interfacial region between two differently oriented W grains.
Most of the Ni impurities concentrate at the GB region.
GB thickness varies upon the level of saturation. (unsaturated:0.3nm,
saturated:0.6nm)
While the mechanical properties (yield stress, ultimate tensile strength,
etc) of Ni-doped W varies by the change of Ni amount and the level of
saturation, the quantitative relation to predict those mechanical properties
are needed.
PROBLEM DESCRIPTION
18. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
(100) (210)W+NI
~0.6 nm
PROBLEM DESCRIPTION
Fully saturated tungsten
GB thickness = 0.6nm
Consist of (100) and (210) orientation of
atom array
J. Luo and et al, 2005, APL
19. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
(a) (c)(b)
(100) (210)W+NI
~0.6 nm
(100) (210)W+NI
~0.3 nm
(100) (210)
Pure W Unsaturated W Saturated W
Setup
20. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
Setup
0.3nm
0.6nm
8 at.%Ni 17 at.%Ni 25 at.%Ni 33 at.%Ni 42 at.%Ni 50 at.%Ni
25 at.%Ni 33 at.%Ni 41 at.%Ni 50 at.%Ni 58 at.%Ni 66 at.%Ni 75 at.%Ni
<100> <210> <100> <210>
<100> <210>
W Ni
W Ni
x
y
z x
y
z
21. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
0.2% Offset
RESULT – (1) PURE W
Typical tungsten properties:
Tensile strength : 1.5 ~ 4.2 GPa
Young’s modulus : 360 ~ 420 GPa
Q.Wei and et al, 2006,
Acta Materialia
4.0 Gpa : Ultimate Tensile
Strength
Yield strength : 1.5 GPa at 0.04 strain
(approximated by 0.2% offset)
22. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
RESULT – (2) UNSATURATED (GB thickness = 0.3 nm)
Yield strength: at strain 0.04
The yield strength has dependent on the
Ni volume fraction.
First peak: at strain 0.12
The first peak’s values has dependent on
the Ni volume fraction.
Second peak: at strain 0.18
The second peak’s values are not depend
on the Ni volume fraction.
Ultimate tensile strength : strain of
0.12~0.18
The maximum tensile strength are not
depend on the Ni volume fraction for the
unsaturated Ni-doped W.
[1] At strain of 0.18
[2] At strain of 0.12
[3] At strain of 0.04
[1]
[2]
[3]
23. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
RESULT – (3) SATURATED (GB thickness = 0.6 nm)
Yield strength: at strain 0.04
The yield strength has dependent on the
Ni volume fraction.
First peak: at strain 0.16
The first peak’s values has dependent on
the Ni volume fraction.
Second peak: at strain 0.24
The second peak’s values have the largest
dependence on the Ni volume fraction.
Ultimate tensile strength : strain of
0.16~0.24
The maximum tensile strength are depend
on the Ni volume fraction for the
saturated Ni-doped W.
[1]
[2]
[3]
[1] At strain of 0.24
[2] At strain of 0.16
[3] At strain of 0.04
24. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
MAX. STRESS
DOS
MAX. STRESS
DOS
Comparison of the maximum tensile stress with the density of states (sum in
the range of -1.3 ~ -1.0 eV) for f-orbital of unsaturated case saturated case
RESULT – Electron DOS
25. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
[ξξ0] [ξ00] [ξξξ] [000][000]
Ν Γ Η Ρ Γ
x
y
Pure W
Unsat.
Sat.
T
L
T
T
L
T
T
L
T
PHONON DISPERSION
26. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
PHONON DISPERSION
Pure W
Unsaturated
Saturated
Pure W
Saturated
Unsaturated
Γ Η ΝΓ
1st transverse curve for the direction of [ξ00], and [ξξ0].
Note that the pure W is idealistic atomic structure based on no GB assumption.
With existing of GB thickness larger than 0, more saturated form gives higher
frequency which is related to the higher bond strength along the horizontal direction.
Although the atomic structure of pure W provides higher phonon frequency in
overall, the stress-strain curve tells us that the substitution of Ni atoms with W plays
a role of compensating the low frequency of phonon dispersion curve.
27. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
Cubic polynomial regressions for (a) total values of E-DOS (electron density of states) of unsaturated
and saturated Ni-added W GB, (b) total values of phonon dispersion in direction of (ξ00) and (ξξ0)
(a) (b)
(ξξ0)
(ξ00)
Saturated
Unsaturated
Trend line
Trend line
RELATION
wgntf
CD
CE
ideal
),(
1max
28. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
UNSATURATED SATURATED
RELATION
A comparisons of the GB strength as a function of Ni atomic fraction using the derived
analytical expression and the CPMD results in the case of 0.3 nm thickness GB, and 0.6 nm
thickness GB
CPMD RESULT
ANALYTICAL
RELATION
CPMD RESULT
ANALYTICAL
RELATION
29910/
max )10(1015.6
1
ww
t
t
e
CD
CE
melt
n
ideal
29. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
400㎛
160㎛
OBTAINING MICROSTRUCTURES
R.W. Margevicius , J. Riedle, P. Gumbsch
(1999). “Fracture toughness of
polycrystalline tungsten under mode I and
mixed mode I/II loading”, Materials
Science and Engineering A, p197-209
-From the tungsten microstructure
morphology in the above paper,
digitalization process has been gone
through to extract grain boundary shape.
-With the assumption that grains are consist
of 3 different orientation and GB to form a
microstructure, grain types are assigned to
grain region.
30. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
DETERMINISTIC FINITE ELEMENT EQUATIONS
2
:δ δ δ δ ,2
V S S Vextint
dV dS dS dV
t
u
s F T Δ T u u
• LaGrangian Kinetics Description
• Finite Element Descretization
M u R
• Solution of Equations (Newmark -Method)
11
1 1
21
1
2
1
2
n n
n n n n
n
n n n n
n n
t
t t
M Ru
u u u u
u u u u
31. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
Type Percentages by Area
GB 7.53 %
Phase1 17.41 %
Phase2 40.43 %
Phase3 34.63 %
For each cases, three different GB properties are applied.
Maximum Tensile strength that is
1. Larger than that of grains
2. Same as that of grains
3. Smaller than that of grains
PERCENTAGE OF EACH PHASES
32. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
FRAMEWORK
V
W (1350 µm)
2H (960 µm)
Pre-Crack
V
1.6µm
1.6µm
All cohesive surfaces serve as potential crack paths.
FE meshes are uniformly structured with “cross-triangle” elements to give maximum
flexibility for resolving crack extensions and arbitrary fracture patterns.
Center-cracked tungsten specimens under tensile loading.
Initial crack : 20 µm
The boundary velocity V (1m/s) is imposed with a linear ramp from zero to V in the
initial phase of loading.
The specimen is stress free and at rest initially.
33. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
COMPARISON FOR COHESIVE ENERGY DISSIPATION
When T = 155 nsec
Low Strength GBMedium Strength GBHigh Strength GB
34. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
COMPARISON FOR CRACK PROPAGATION DIRECTION
When t = 155 nsec
Low Strength GB
Medium Strength GBHigh Strength GB
35. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
High Strength GB Medium Strength GB
Low Strength GB
Primary crack
Micro crack
Primary crack
Micro crack
Primary crack
Micro crack
COMPARISON OF PRIMARY CRACK AND MICROCRACKS
36. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
CD
2
h
ba
5.21CE
Therefore, can be explained as energy
dissipation per unit crack length or crack density. C is a constant.
C
h
ba
2
a
b
CD
In our case of simulation, C = 12.5
By substituting the equation to the above equation,
we obtained a relation of
max
2
CD
h
ba
2
max
2
25CE
THE RELATION BETWEEN ENERGY DISSIPATION VS CRACK DENSITY
37. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
CD
h
ba
2
max
2
25CE
THE RELATION BETWEEN ENERGY DISSIPATION VS CRACK DENSITY
38. Interfacial Multiphysics Lab (https://engineering.purdue.edu/~tomar)
CONCLUSIONS
Analyses demonstrate that the failure of a tungsten involves inter-granular cracks, intra-granular
cracks, and significant microcracking.
By applying different properties of GBs, plots of cohesive energy dissipation display various
patterns of energy release. Property of ductility and brittleness are known as temperature dependent,
however, the findings in this study indicates that the tungsten microstrucutural failure can have
both ductile and brittle pattern of failure decided also by property of GBs. (GBs have 7.53% by
volume)
The level of microcracking goes greater in the interfaces of grains as strength of GBs becomes
lower.
A significant microcracking occurs during failure. Surface energy study in this research indicates
m value to be around 14 for such microstructure with no time dependent. This finding can
contribute to predict the level of microcrack over primary crack at other time frames.
In literature, continuum and analytical fracture mechanics work usually neglects contribution of
GBs to overall microstructural fracture strength. The findings in this work indicate property of GB
act major role in crack propagation pattern as well as crack initiation time.