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SSRN 2024年

作者： Li, Rui Torun, Serdar Santiago, Jacob Salas, Daniel Karaman, Ibrahim Ross, Joseph H. Department of Physics and Astronomy Texas A&M University 578 University Dr. College StationTX77843 United States Department of Materials Science and Engineering Texas A&M University 575 Ross St College StationTX77843 United States

In this study, we investigated Hf and Zr substituted nitinol shape memory alloys using Nuclear magnetic Resonance (NmR) spectroscopy, focusing on alloys tuned by thermal processing for martensite-transforming and non-transforming behavior. Ni50.75Ti29.25Zr20 and Ni50.3Ti29.7Hf20 non-transforming samples were found to exhibit a glass transition, shown very clearly in NmR by the development of large random local strains, despite no evidence for transformation in X-ray crystallography or calorimetry. These nontransforming samples maintain electronic similarity to the B2 cubic phase, indicating that the strain nano-domains are not locally equivalent to martensite. Using NmR relaxation measurements as a highly sensitive probe into kHz and mHz scale dynamical strains, in a NiTiHf sample tuned for strain glass behavior we identified non-Vogel Fulcher dynamical behavior, with rapidly fluctuating local strains developing in the high temperature strainliquid regime, accompanied by the gradual disappearance of quasi-static dynamics above and below the glass freezing point. Notably, the results also show a clear difference between the dynamical behavior of the strain glass and a NiTiZr non-transforming sample with greater defect density, which exhibits frozen random strain below a well-defined transformation point but without the appearance of any strain-glass dynamics. This demonstrates the possibility for defect driven nanodomain distortions with no strain-glass behavior. These findings highlight the ability of NmR as a powerful tool for investigating the dynamics and local structures in these materials. © 2024, The Authors. All rights reserved.

关键词： Nuclear magnetic resonance spectroscopy

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Efficient Propagation of Uncertainty via Reordering monte Carlo Samples

arXiv

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arXiv 2023年

作者： Khatamsaz, Danial Attari, Vahid Arróyave, Raymundo Allaire, Douglas L. Dept. of Mechanical Engineering Texas A&m University College StationTX77843 United States Dept. of Materials Science and Engineering Texas A&m University College StationTX77843 United States

Uncertainty analysis in the outcomes of model predictions is a key element in decision-based material design to establish confidence in the models and evaluate the fidelity of models. Uncertainty Propagation (UP) is a technique to determine model output uncertainties based on the uncertainty in its input variables. The most common and simplest approach to propagate the uncertainty from a model inputs to its outputs is by feeding a large number of samples to the model, known as monte Carlo (mC) simulation which requires exhaustive sampling from the input variable distributions. However, mC simulations are impractical when models are computationally expensive. In this work, we investigate the hypothesis that while all samples are useful on average, some samples must be more useful than others. Thus, reordering mC samples and propagating more useful samples can lead to enhanced convergence in statistics of interest earlier and thus, reducing the computational burden of UP process. Here, we introduce a methodology to adaptively reorder mC samples and show how it results in reduction of computational expense of UP processes. © 2023, CC BY.

关键词： Uncertainty analysis

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A preliminary evaluation of the computational fluid dynamics capabilities in moose 28

A preliminary evaluation of the computational fluid dynamics...

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2021 28th International Conference on Nuclear engineering, ICONE 2021

作者： Weiss, Abdullah G. Abdoelatef, m. Gomaa Bani Ahmad, mohammad T. H. Ahmed, Karim Kimber, mark L. Department of Nuclear Engineering Texas A&M University College StationTX77840 United States Department of Materials Science and Engineering Texas A&M University College StationTX77840 United States

ISBN: (纸本)9780791885260

The multiphysics Object Oriented Simulation Environment (mOOSE) is a code package that couples a variety of physics modules, allowing for highly accessible multiphysics simulations. The physics modules include a finite-element Navier-Stokes (N-S) module that is designed to solve laminar fluid dynamics problems. The usage of this module in multiple recent studies coupled with the growing interest in mOOSE for usage in non-LWR safety studies by the Nuclear Regulatory Commission (NRC) prompted the authors to investigate the computational fluid dynamics (CFD) capabilities of mOOSE. A 2D flow past a round cylinder scenario is simulated in the mOOSE environment to investigate the effectiveness of the N-S module. The simulation assumed an unsteady laminar flow with a Reynolds number of 200, where the unsteadiness in the vortex street is captured using a Euler-implicit time-integration scheme. To verify the results from mOOSE, a similar simulation is conducted using the well-utilized OpenFOAm finite volume code, and the velocity profiles of both transient simulations are compared. Grid and input sensitivity studies are conducted in mOOSE to quantify the numerical and input errors, respectively. The numerical and input errors are also visualized with contour plots in order to qualitatively understand the evolution of the errors across time and space. Results show that mOOSE struggles with capturing the instabilities in the flow, as it takes more than 20 seconds before a vortex street is observed. Excellent agreement in the velocities is seen between mOOSE and OpenFOAm upstream of the cylinder, but huge discrepancies can be seen where instabilities are expected around the cylinder and upstream of it. The discrepancies become more severe as the transient simulations progress in time. The numerical error is most prominent in the wake of the cylinder and around the boundaries of the channel. The input errors are also prominent in the wake but are most prominent around the cylind

关键词： multiphysics

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On the equilibrium limit of liquid stability in pressurized aqueous systems

arXiv

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arXiv 2024年

作者： Zarriz, Arian Journaux, Baptiste Powell-Palm, matthew J. J. Mike Walker’66 Department of Mechanical Engineering Texas A&M University College StationTX United States Department of Department of Earth and Space Sciences University of Washington SeattleWA United States Department of Materials Science & Engineering Texas A&M University College StationTX United States Department of Biomedical Engineering Texas A&M University College StationTX United States

Phase stability, and the limits thereof, are a central concern of materials thermodynamics. However, the temperature limits of equilibrium liquid stability in chemical systems have only been widely characterized under constant (typically atmospheric) pressure conditions, whereunder these limits are represented by the eutectic. At higher pressures, the eutectic will shift in both temperature and chemical composition, opening a wide thermodynamic parameter space over which the absolute limit of liquid stability, i.e., the limit under arbitrary values of the thermodynamic forces at play (here pressure and concentration), might exist. In this work, we use isochoric freezing and melting to measure this absolute limit for the first time in several binary aqueous brines, and nodding to the etymology of "eutectic", we name it the "cenotectic" (from Greek "κοινός-τŉξĭς", meaning "universal-melt"). We discuss the implications of our findings on ocean worlds within our solar system and cold ocean exoplanets;estimate thermodynamic limits on ice crust thickness and final ocean depth (of the cenotectic or "endgame" ocean) using measured cenotectic pressures;and finally provide a generalized thermodynamic perspective on (and definition for) this fundamental thermodynamic invariant point. © 2024, CC BY-NC-ND.

关键词： Eutectics

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NmR study of Ni50+xTi50-x Strain-Glass

arXiv

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arXiv 2023年

作者： Li, Rui Santiago, Jacob Salas, Daniel Karaman, Ibrahim Ross, Joseph H. Department of Physics and Astronomy Texas A&M University College StationTX77843 United States Department of Materials Science and Engineering Texas A&M University College StationTX77843 United States

We studied Ni50+xTi50-x with compositions up to x = 2, performing 47Ti and 49Ti nuclear magnetic resonance (NmR) measurements from 4 K to 400 K. For large x in this system, a strain-glass appears in which frozen ferroelastic nano-domains replace the displacive martensite structural transition. Here we demonstrate that NmR can provide an extremely effective probe of the strain glass freezing process, with large changes in NmR line-shape due to the effects of random strains which become motionally narrowed at high temperatures. At the same time with high-resolution x-ray diffraction we confirm the lack of structural changes in x ≥ 1.2 samples, while we show that there is little change in the electronic behavior across the strain glass freezing temperature. NmR spin-lattice relaxation time (T1) measurements provide a further measure of the dynamics of the freezing process, and indicate a predominantly thermally activated behavior both above and below the strain-glass freezing temperature. We show that the strain glass results are consistent with a very small density of critically divergent domains undergoing a Vogel-Fulcher-type freezing process, coexisting with domains exhibiting faster dynamics and stronger pinning. Copyright © 2023, The Authors. All rights reserved.

关键词： Nuclear magnetic resonance

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First Principles Computational Study of Caso4∙Xh2o Dissolution

SSRN

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SSRN 2023年

作者： Blanco, Brayan Alberto Arenas Cleveland, mack Balbuena, Perla B. Bullard, Jeffrey W. Department of Chemical Engineering Texas A&M University College StationTX77843 United States Department of Materials Science and Engineering Texas A&M University College StationTX77843 United States Department of Chemistry Texas A&M University College StationTX77843 United States Zachry Department of Civil and Environmental Engineering Texas A&M University College Station77843 United States

Calcium sulfate can be found in any of three hydration states, CaSO4∙xH2O where x = 0 (anhydrite), 0.5 (bassanite), or 2 (gypsum). Each has different crystallographic structure, solubility, and dissolution rate in water. Despite the large number of experimental studies of their dissolution, relatively little is known at the atomistic level. We investigate their dissolution by ab initio molecular Dynamics (AImD) simulations. We evaluate detachment of Ca2+ and SO42- ions from the (100), (001) and (010) surfaces of anhydrite, bassanite, and gypsum, respectively, with various vacancies and defects. The energy required to remove a calcium atom is greater than that to remove the sulfate group for all three minerals, indicating that calcium detachment can be the rate-controlling step of the process. The impact of surface vacancies on the hydration of each phase was investigated, and we observe that a sulfate vacancy is required for spontaneous hydration of the corresponding phase. © 2023, The Authors. All rights reserved.

关键词： Dissolution

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An Efficient Finite Difference-based Implicit Solver for Phase-Field Equations with Spatially and Temporally Varying Parameters

arXiv

引用

arXiv 2024年

作者： mao, Zirui Liu, G.R. Demkowicz, michael J. Department of Materials Science and Engineering Texas A&M University College StationTX77843 United States Department of Aerospace Engineering and Engineering Mechanics University of Cincinnati CincinnatiOH45221 United States

The phase field method is an effective tool for modeling microstructure evolution in materials. many efficient implicit numerical solvers have been proposed for phase field simulations under uniform and time-invariant model parameters. We use Eyre's theorem to develop an unconditionally stable implicit solver for spatially non-uniform and time-varying model parameters. The accuracy, unconditional stability, and efficiency of the solver is validated against benchmarking examples. In its current form, the solver requires a uniform mesh and may only be applied to problems with periodic, Neumann, or mixed periodic/Neumann boundary conditions. Copyright © 2024, The Authors. All rights reserved.

关键词： Finite difference method

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Adaptive Loss Weighting for machine Learning Interatomic Potentials

arXiv

引用

arXiv 2024年

作者： Ocampo, Daniel Posso, Daniela Namakian, Reza Gao, Wei J. Mike Walker '66 Department of Mechanical Engineering Texas A&M University College StationTX77843 United States Department of Mechanical Engineering The University of Texas at San Antonio San AntonioTX78249 United States Department of Materials Science & Engineering Texas A&M University College StationTX77843 United States

Training machine learning interatomic potentials often requires optimizing a loss function composed of three variables: potential energies, forces, and stress. The contribution of each variable to the total loss is typically weighted using fixed coefficients. Identifying these coefficients usually relies on iterative or heuristic methods, which may yield sub-optimal results. To address this issue, we propose an adaptive loss weighting algorithm that automatically adjusts the loss weights of these variables during the training of potentials, dynamically adapting to the characteristics of the training dataset. The comparative analysis of models trained with fixed and adaptive loss weights demonstrates that the adaptive method not only achieves a more balanced predictions across the three variables but also improves overall prediction accuracy. © 2024, CC BY.

关键词： machine learning

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Accelerated multi-Objective Alloy Discovery Through Efficient Bayesian methods: Application to the FCC High Entropy Alloy Space

SSRN

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SSRN 2025年

作者： Hastings, Trevor mulukutla, mrinalini Khatamsaz, Danial Salas, Daniel Xu, Wenle Lewis, Daniel Person, Nicole Skokan, matthew miller, Braden Paramore, James Butler, Brady Allaire, Douglas Attari, Vahid Karaman, Ibrahim Pharr, George m. Srivastava, Ankit Arróyave, Raymundo Department of Materials Science and Engineering College StationTX77843-3003 United States DEVCOM Army Research Laboratory South at Texas A&M University College StationTX77843-3003 United States Texas A&M University Department of Mechanical Engineering College StationTX77843 United States

This study introduces BIRDSHOT, an integrated Bayesian materials discovery framework designed to efficiently explore complex compositional spaces while optimizing multiple material properties. We applied this framework to the CoCrFeNiVAl FCC high entropy alloy (HEA) system, targeting three key performance objectives: ultimate tensile strength/yield strength ratio, hardness, and strain rate sensitivity. The experimental campaign employed an integrated cyber-physical approach that combined vacuum arc melting (VAm) for alloy synthesis with advanced mechanical testing, including tensile and high-strain-rate nanoindentation testing. By incorporating batch Bayesian optimization schemes that allowed the parallel exploration of the alloy space, we completed five iterative design-make-test-learn loops, identifying a non-trivial three-objective Pareto set in a high-dimensional alloy space. Notably, this was achieved by exploring only 0.15% of the feasible design space, representing a significant acceleration in discovery rate relative to traditional methods. This work demonstrates the capability of BIRDSHOT to navigate complex, multi-objective optimization challenges and highlights its potential for broader application in accelerating materials discovery. © 2025, The Authors. All rights reserved.

关键词： Tensile testing

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Synergistic and Antagonistic Interaction between Zddp and Tio2 Nanoparticles Under Boundary Lubrication

SSRN

引用

SSRN 2024年

作者： Sharma, Vinay Timmons, Richard B. Erdemir, Ali Aswath, Pranesh B. Materials Science and Engineering University of Texas at Arlington ArlingtonTX76019 United States Chemistry and Biochemistry University of Texas at Arlington ArlingtonTX United States Department of Mechanical Engineering Texas A&M University College StationTX United States

Lubricants are mixtures of additives that serve multiple purposes, and these additives must work synergistically at best and at worst, not interfere with each other. We have shown that when nanoparticles of TiO2 and ZDDP are used together they act antagonistically. When used sequentially, we see a range of outcomes from very synergistic interaction when TiO2 is used first followed by ZDDP wherein TiO2 reacts with the Fe substrate to form FeTiO3, a superior surface layer where medium and long chain Zn-polyphosphates and Ti-phospate tribofilms form due to the decomposition of ZDDP under tribological conditions. On the other hand, when use of ZDDP is followed by TiO2 we see outcomes that favor the shorter duration of use of ZDDP. © 2024, The Authors. All rights reserved.

关键词： Titanium dioxide

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