About

Rachel K Miller, M.D., is a Professor of Clinical Medicine specializing in Geriatrics at the University of Pennsylvania. She serves as a Staff Physician in Geriatrics & Home-Based Primary Care at the Philadelphia CMC-VA Medical Center and holds the position of Vice Chief of Education in the Division of Geriatrics within the Department of Medicine. Her educational background includes a BA from Rutgers University (2000), an MD from the University of Medicine and Dentistry of New Jersey (2003), and a Master’s in Education from the University of Pennsylvania (2014). Her professional focus encompasses geriatrics, home-based primary care, and medical education, with a particular emphasis on teaching strategies for the care of older adults and the integration of social and structural determinants of health into geriatric training.

Research topics

• Materials science
• Computer science
• Physics
• Condensed matter physics
• Statistical physics

Selected publications

• High-Throughput Screening for Practical Applications of Metal–Organic Frameworks to Advanced Water-Based Thermal Storage Technologies

  ACS Applied Materials & Interfaces · 2026-04-20

  articleSenior authorCorresponding

  The development of efficient adsorbents for water-based adsorption thermal energy storage (ATES) is essential for the large-scale utilization of low-cost and renewable energy, as the performance of these systems highly depends on the choice of adsorbent-water working pair. While metal–organic frameworks (MOFs) have attracted significant attention for thermal energy storage applications, a systematic evaluation of their suitability as adsorbents for water-based ATES remains limited. In this study, we intend to employ high-throughput screening (HTCS) combined with advanced Monte Carlo simulations to systematically screen the experimentally synthesized MOFs included in the novel MOSAEC-DB for the application in our in-house prototype ATES tank. MOSAEC-DB is the most accurate MOFs database, comprising error-free crystal structures and density functional theory (DFT) fitted partial charges. A large number of MOFs are identified that exhibit excellent performance when benchmarked against the current state-of-the-art zeolite materials in a specific application. Based on the performance assessment metrics, including the energy density (hTES), working capacity (Δn), and regenerability (R%), six top performers are selected for their extraordinary adsorbent-water working-pair performance. These top-listed candidates exhibit outstanding thermal stability above 523.15 K (250 °C), as reported in the corresponding literature. The obtained hTES of the best-performing candidates is over 450 kWh/m3, while commonly used Zeolites (13X and 4A) exhibit between 200 and 400 kWh/m3, depending on operating conditions. This systematic analysis provides a clear recommendation for the bulk synthesis of these MOFs and their subsequent evaluation in practical, real-world ATES experiments.

  PublisherDOI

• Framework Flexibility-Driven H ₂ O Diffusion in MOF-303; Mechanistic Insights from Machine-Learned Interatomic Potentials

  The Journal of Physical Chemistry C · 2026-04-14

  articleSenior authorCorresponding

  A metal organic framework, namely MOF-303, has emerged as a promising sorbent for water harvesting applications; however, the intrinsic diffusion mechanism of adsorbed H2O molecules, crucial for reticular design of such materials, is still unknown. The computational prediction of thermodynamic properties of H2O in MOF-303 has become a common practice, but most existing literature neglects the dynamic behavior in the flexible framework. Moreover, the limitations of classical force fields fail in accurately describing vibrational states, imposing a major bottleneck in achieving realistic dynamics. In this study, we present a methodology for achieving a chemically accurate diffusion mechanism in a fully flexible framework. The methodology employs highly accurate and efficiently trained deep machine learned interatomic potentials (DP-MLIP) and molecular dynamics simulations. Accurate diffusion coefficients for H2O in flexible MOF-303 are obtained with the DP-MLIP, and the associated dynamic behavior is benchmarked against the density functional theory method (DFT) and recently reported generic foundation model (MACE) in nudged elastic band (NEB) calculations. Analysis shows close approximations in diffusion barriers predicted by DP-MLIP, DFT, and MACE, indicating these approaches capture the same sequence of adsorption-state stability. In contrast, the diffusion barrier obtained from the classical force field deviates substantially from the reference DFT. H2O molecules exhibit a higher self-diffusion coefficient (∼10×) in MD with the DP-MLIP model than the classical potential. The atomistic simulations with our trained MLIP enable a more accurate and efficient computational evaluation of the dynamic behavior of H2O molecules in flexible MOF-303, offering a new opportunity for rational design of materials with comparable flexibility.

  PublisherDOI

• A new TRNSYS Type for solid-gas adsorption thermal energy storage reactors: Implementation, validation, and parametric performance assessment of a simplified adsorption-based space-heating system

  Journal of Energy Storage · 2026-04-27

  articleOpen access

  Adsorption-based thermal energy storage (ATES) offers a promising solution to mitigate the temporal mismatch between solar energy availability and residential heating demand. However, its adoption in built environments remains limited mainly due to the lack of comprehensive evaluations of long-term operation and transient behaviour at the system level, particularly when integrated with solar and building subsystems. This study presents the development, validation, and system-level integration of a novel TRNSYS component, Type 2802, designed to simulate the transient thermal behaviour of solid-gas ATES reactors using water vapour as the adsorbate. A detailed mathematical model is implemented in FORTRAN and embedded within TRNSYS. The model is experimentally validated using both data from the literature for small- and large-scale zeolite 13X reactors and in-house discharging tests with zeolite 5A and activated carbon. The model demonstrates strong predictive accuracy across diverse conditions. The resulting TRNSYS Type 2802 is general in the sense that it can easily be used to investigate different adsorbent materials, cylindrical reactor geometries, insulation effectiveness, and inlet conditions. Beyond validation, Type 2802 configured with zeolite 13X, is tested in an integrated simulation scenario using a simplified ATES system designed to meet residential space heating demand. Parametric investigations are carried out to examine the influence of charging, tank loop flow rates, and the addition of a heat recovery unit on the zeolite energy storage density (ESD) and system coefficient of performance (COP). Results reveal four optimal operating scenarios, with the highest ESD (122.83 kWh/m 3 ) and COP (0.164) achieved under the lowest flow rate conditions in the baseline model (without an HRU). Incorporating an HRU with 0.8 effectiveness improves the ESD by up to 40% and increases the COP from 0.164 to 0.337. • A new TRNSYS Type is developed to simulate solid–gas adsorption thermal storage reactors. • The model is validated against literature data and in-house experimental results. • The TRNSYS Type is integrated into a wider solar-driven heating system model. • System performance is assessed under varying air and heat transfer fluid flow rates. • Incorporating a heat recovery unit greatly enhances energy storage density and COP.

  PublisherDOI

• Application of Enhanced Gurson-Like Ductile Damage Models to Simulate Crack Growth in Pipeline Steels Under Wide Range of Constraint Conditions

  2025-07-20

  article

  Abstract For the safe design and operation of high-performance pipelines, it is important to characterize the crack growth behaviors (using J-R curves) for pipeline steels under a variety of constraint conditions, so that reliable pipeline integrity assessments can be performed. The finite element method (FEM) based on an enhanced Gurson-like ductile damage model was used to investigate the ductile crack growth behaviors on pipeline steels. The standard Gurson-Tvergaard-Needleman (GTN) model cannot account for several ductile damage anisotropies. This limitation narrows the applicability of the GTN model to constraint conditions similar to the data used to calibrate the model. It is demonstrated in the present study that the implemented enhanced model significantly improves upon the GTN model and can accurately predict the ductile fracture behavior over a wide range of constraint conditions based on limited calibration data. The ductile damage model was used to analyze ductile crack growth behaviors in single-edge notched bending (SENB) and single-edge notched tension (SENT) specimens. Several SENT crack geometries were analyzed, representing a wide range of constraint conditions. The numerically calculated crack growth resistance curves were compared to the experimental J-R curves and curves developed using the original GTN model.

  PublisherDOI

• An Integrated Computational Fluid Dynamics and Chemical Kinetics Modelling for Predicting Oil Degradation in Maritime Diesel Engines

  SSRN Electronic Journal · 2025-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Spectral Characterization of Additive-Modified Lubricant Systems for Optical Sensing Applications

  2025-01-01

  articleSenior author

  We apply a spectral method to evaluate viscosity changes in oil-additive systems. Using UV-Vis data and Maxwell–Garnett modeling, we demonstrate a pathway for optical sensing of lubricant condition via dielectric response.

  PublisherDOI

• Local Order Average-Atom Interatomic Potentials

  ArXiv.org · 2025-10-07

  preprintOpen access

  This article describes an extension to the effective Average Atom (AA) method for random alloys to account for local ordering (short-range order) effects by utilizing information from partial radial distribution functions. The new Local-Order Average Atom (LOAA) method is rigorously derived based on statistical mechanics arguments and validated for non-stoichiometric binary 2D hexagonal crystals and 3D FeNiCr and NiAl alloys whose ground state is obtained through Monte Carlo sampling. Material properties for these alloys, and phase transformations for the NiAl system, computed from static and dynamic atomistic simulations using standard interatomic potentials (IPs) exhibit a strong dependence on local ordering that is captured by simulations with effective LOAA IPs, but not the original AA method. The advantage of LOAA is that it requires smaller system sizes to achieve statistically converged results and therefore enables the simulation of complex materials, such as high-entropy alloys, at a fraction of the computational cost of standard IPs.

  PublisherOA PDFDOI

• Numerical simulation of ductile damage in pipeline steels across different constraint conditions using a combined void growth and coalescence model

  Engineering Fracture Mechanics · 2025-03-12 · 2 citations

  articleOpen accessCorresponding

  • Novel implementation of a two-surface Gurson-like ductile damage model. • Model incorporates various anisotropic aspects of ductile fracture. • Model used to simulate ductile fracture in pipeline steels. • Fracture test specimens under a wide range of constraint conditions simulated. • Better performance compared to existing models like GTN model. Finite element method (FEM) simulations using a two-surface Gurson-like ductile damage model were used to investigate the ductile crack growth behaviors on X80 and X100 pipeline steels, under a wide range of constraint conditions. The implemented approach combines models in the spirit of the Gologanu-Leblond-Devaux (GLD) and Thomason’s models to create a combined void growth and coalescence model. The implemented model can account for several ductile damage anisotropies which cannot be accommodated by the widely used standard Gurson-Tvergaard-Needleman (GTN) model, which is limited to constraint conditions similar to the data used to calibrate the model. It is demonstrated in the study that the implemented combined model significantly improves upon the GTN model and can accurately predict the ductile fracture behavior over a wide range of constraint conditions based on the same calibration data. The ductile damage model was used to analyze ductile crack growth behaviors in single-edge notched bending (SENB) and single-edge notched tension (SENT) specimens. Three different pipeline steels were studied. A wide range of SENT crack geometries were analyzed. These specimens represented a wide range of constraint conditions. The numerically calculated crack growth resistance curves were compared to experimental J - Δ a curves and curves developed using the GTN model.

  PublisherDOI

• Status of the ALS-U project to create a soft x-ray diffraction limited light source

  Journal of Physics Conference Series · 2025-05-01

  articleOpen access

  Abstract The ALS-U project to upgrade the Advanced Light Source to a multi bend achromat lattice received CD-3 approval in 2022 marking the start of the construction phase for the Storage Ring. Construction of the accumulator under a prior CD-3A authorization is already well advanced. ALS-U promises to deliver diffraction limited performance in the soft x-ray range by lowering the horizontal emittance to about 70 pm rad resulting in two orders of magnitude brightness increase for soft x-rays compared to the current ALS. The design utilizes a nine bend achromat lattice, with reverse bending magnets and on-axis swap-out injection utilizing an accumulator ring. It is optimized to produce intense beams of soft x-rays, which offer spectroscopic contrast, nanometer-scale resolution, and broad temporal sensitivity. This paper presents the final design, prototype results as well as construction progress.

  PublisherDOI

• Compact Coaxial Variable Resistance Load with Integrated Voltage and Current Probes for Evaluation of High Voltage and Current Pulses with Fast Risetime

  2025-06-15

  article1st authorCorresponding

  IS4S has built and tested a compact coaxial geometry variable resistance load using a fixed geometry Copper Sulfate resistor. The resistance of the load can be chosen by setting the Copper Sulfate concentration. The load is designed for changing resistance without disassembling the load and with an integrated air bleed mechanism to remove all air bubbles out of the Copper Sulfate for consistent performance of the load resistance. A Prodyn FD-5 D-dot voltage probe and IS4S designed compensated Rogowski coil are integrated into the load for measurement. The instrumented load is designed for measuring pulses <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt;500 \text{kV}$</tex> in peak voltage and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt;10 \text{kA}$</tex> peak current with a risetime <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&lt;5 \text{ns}$</tex>. The load is of a compact coaxial design and an impedance of 50 ohms is achievable including consideration of the load impedance separate from resistance of the Copper Sulfate.

  PublisherDOI

Frequent coauthors

• Peter D. Blair

  George Mason University

  68 shared

• Ellad B. Tadmor

  University of Minnesota

  53 shared

• Mark A. Miller

  36 shared

• James Barnard

  University of Nevada, Reno

  36 shared

• A. Slingo

  36 shared

• G. J. Robinson

  36 shared

• Connor Flynn

  University of Oklahoma

  36 shared

• Thomas P. Ackerman

  University of North Carolina School of the Arts

  36 shared

Labs

• Rachel K Miller LabPI